我正在尝试将在NodeJS中处理的文本文件流式传输到浏览器。
以下是处理前的文本文件。
该文件名为dbUsers.json。
{"userId":443,"email":"bob@gmail.com","hashedPassword":"36583a77a098c02ef111e2f2521d77b58e420f2bc7e9bf930ec24b21d42ea2e0","timeStamp":1567439821109,"deleted":false}
{"userId":447,"email":"alice@gmail.com","hashedPassword":"36583a77a098c02ef111e2f2521d77b58e420f2bc7e9bf930ec24b21d42ea2e0","timeStamp":1567439909013,"deleted":false}
{"userId":451,"email":"cliff@gmail.com","hashedPassword":"36583a77a098c02ef111e2f2521d77b58e420f2bc7e9bf930ec24b21d42ea2e0","timeStamp":1567443638340,"deleted":false}
...
处理后，我可以使用以下命令将数据流式传输到NodeJS服务器上的新文件中：
// Create a writable stream and specify the file which will receive the data from the readable stream.
let destinationStream = fs.createWriteStream(_data.baseDir + '/dbPermissions/dbUsers' + '/' + 'test' + '.txt', {flags : 'a'});
pipeline
(
sourceStream,
destinationStream,
function(error){if(error){console.log('There was an error.');}}
);
新文件显示按预期处理的数据。
一些字段已删除，标记为删除的记录也已删除。
这说明sourceStream在NodeJS中起作用。
现在，新文件中的数据如下：
{"userId":443,"email":"bob@gmail.com","timeStamp":1567439821109}
{"userId":447,"email":"alice@gmail.com","timeStamp":1567439909013}
{"userId":451,"email":"cliff@gmail.com","timeStamp":1567443638340}
...
在将SourceStream流传输到客户端浏览器之前，将其记录到NodeJS控制台会产生以下输出。
Readable {
_readableState:
ReadableState {
objectMode: false,
highWaterMark: 16384,
buffer: BufferList { head: [Object], tail: [Object], length: 45 },
length: 3035,
pipes:
WriteStream {
_writableState: [WritableState],
writable: true,
domain: null,
_events: [Object],
_eventsCount: 6,
_maxListeners: undefined,
path:
'C:\\Users\\user\\Desktop\\Tutorials\\iotajs\\ias\\accounting\\/dbPermissions/dbUsers/test.txt',
fd: null,
flags: 'a',
mode: 438,
start: undefined,
autoClose: true,
pos: undefined,
bytesWritten: 0,
closed: false },
pipesCount: 1,
flowing: true,
ended: true,
endEmitted: false,
reading: false,
sync: true,
needReadable: false,
emittedReadable: true,
readableListening: false,
resumeScheduled: true,
paused: false,
emitClose: true,
destroyed: false,
defaultEncoding: 'utf8',
awaitDrain: 0,
readingMore: true,
decoder: null,
encoding: null },
readable: true,
domain: null,
_events:
[Object: null prototype] {
close: [ [Function], [Function: onclose] ],
end: [ [Function: onend], [Function] ],
finish: [Function: onfinish],
error: [Function: onerror],
data: [Function: ondata] },
_eventsCount: 5,
_maxListeners: undefined }
Returning this response: 200
Returning this response: 200
将sourceStream流传输到浏览器，然后注销到浏览器的控制台时，输出与上面相同。
因此，我确定sourceStream可以完整地到达客户端。
我需要使用的数据可能被锁定在许多 上面对象的缓冲区属性，现在在上面称为responseTextStream 客户端浏览器。
我的问题是我不知道如何访问 缓冲区，我也不知道如何将它们从数字转换回文本。
以下是我希望的客户端浏览器中的功能 使用缓冲区中的数据。这是我需要帮助的地方-我不知道如何访问信息流。谢谢，约翰
// Populate the dbUsersList webpage with user records.
app.loadUsersListPage = function()
{
// Ask the server for the JSON records found in the dbUsers file.
// Then run the callback function defined here which inserts rows into the usersListTable on the webpage
// and populates them with data from the file of JSON records returned.
app.client.request(undefined,'api/aUsers','GET',QueryStringObject,undefined,function(statusCode,responseTextStream)
{
// if the call to handlers._users.get which is mapped to api/aUsers called back success.
if(statusCode == 200)
{
// The streamed data can be seen on the console as a buffer full of numbers
console.log(responseTextStream._readableState.buffer.head.data.data);
// Create a handle which can be used to manipulate the table on the webpage.
var table = document.getElementById("usersListTable");
// The pseudocode below does not work but is shows what I hope to accomplish.
// The line below does not help to access the stream. This is where I need help.
// What line or lines of code would facilitate access to the stream and allow
// processing it as a string, character by character, as shown below.
var Astr = responseTextStream;
var line = "";
for(var i=0; i<Astr.length; i++)
{
var chr = String.fromCharCode(Astr[i]);
if(chr == "\n" || chr == "\r")
{
// Look at each line of json at the console as it is consumed.
console.log("line: ",line);
// Turn the line, which is a json string, back into a json object
var recordObject = JSON.parse(line);
if(recordObject)
{
// Insert a new row in the table.
var tr = table.insertRow(-1);
// Make the new row a member of the class 'checkRow'
tr.classList.add('checkRow');
// Insert five new cells into the new row.
var td0 = tr.insertCell(0);
var td1 = tr.insertCell(1);
var td2 = tr.insertCell(2);
var td3 = tr.insertCell(3);
// load the new cells with data from the recordObject.
td0.innerHTML = recordObject.userId;
td1.innerHTML = recordObject.email;
td2.innerHTML = recordObject.timeStamp;
td3.innerHTML = '<a href="/users/edit?email=' + recordObject.userId + '">View / Edit / Delete</a>';
} // End of: if(recordObject)
// clear the line buffer to start the next line.
line = "";
} // End of: if(chr == "\n" || chr == "\r"){do stuff}
else
{
line += chr;
}
}; // End of: for(var i=0; i<Astr.length; i++){...}
} // End of: if the call to handlers._users.get which is mapped to api/aUsers called back successfully.
}); // End of: app.client.request(undefined,'api/checks','GET'...
} // End of: app.loadUsersListPage = function(){...}
// End of: Populate the dbUsersList webpage with user records.
根据@Brad的回答，我将他的代码与 结果不令人满意。下面是Brad的代码，下面是 由他的代码在
value处返回的对象 登录到控制台。与缓冲区之前的对象相同 扩大了考试范围。我的问题仍然是返回的对象 只是一堆包含一堆数字而不是 我可以做的事情的字符串。将value登录到 控制台，我希望能看到人类修改过的数据的每一行 可读格式。我在做什么，或者我在做什么错？ 谢谢，约翰
// Populate the dbUsersList webpage with user records.
app.loadUsersListPage = async function()
{
// Define which users will be retrieved from dbUsers.json
// This is not being used for now so all records will be retrived.
var QueryStringObject = {};
// Define a client function that calls for data from the server.
const fetchPromise = fetch('api/aUsers')
.then
(
(res) =>
{
// Verify that we have some sort of 2xx response that we can use
if (!res.ok)
{
throw res;
}
// If no content, immediately resolve, don't try to parse JSON
if (res.status === 204)
{
return;
}
// Initialize variable to hold chunks of data as they come across.
let textBuffer = '';
// This does not seem to be used. Delete this after everything else is working.
const self = this;
// Process the stream.
return res.body
// Decode as UTF-8 Text
.pipeThrough
(
new TextDecoderStream()
)
// Split on lines
.pipeThrough
(
new TransformStream
(
{
transform(chunk, controller)
{
textBuffer += chunk;
const lines = textBuffer.split('\n');
for (const line of lines.slice(0, -1))
{
controller.enqueue(line);
} // End of: for (const line ...)
textBuffer = lines.slice(-1)[0];
}, // End of: Transform(chunk, controller){do stuff}
flush(controller)
{
if (textBuffer)
{
controller.enqueue(textBuffer);
} // End of: if (textBuffer)
} // End of: flush(controller){do stuff}
} // End of: parameters for new TransformStream
) // End of: call to constructor new TransformStream
) // End of: parameters for pipeThrough - Split on lines
// Parse JSON objects
.pipeThrough
(
new TransformStream
(
{
transform(line, controller)
{
if (line)
{
controller.enqueue
(
JSON.parse(line)
); //End of: call to controller.enqueue function
} // End of: if (line)
} // End of: transform function
} // End of: parameter object for new TransformStream
) // End of: new TransformStream parameters
); // End of: parameters for .pipeThrough - Parse JSON objects
} // End of: .then callback function instruction for fetch
); // End of: .then callback parameters for fetch
// Call to function which asks server for data.
const res = await fetchPromise;
const reader = res.getReader();
function read()
{
reader.read()
.then
(
({value, done}) =>
{
if (value) {
// Your object will be here
console.log('I got to this point');
console.log(value);
}
if (done) {
return;
}
read();
}
);
}
read();
} // End of: app.loadUsersListPage = function(){...}
// End of: Populate the dbUsersList webpage with user records.
这是当Brad的代码将
value登录到控制台时得到的。它是 我之前得到的同样的东西。我希望看到文本行。什么 我在做什么，或者我在做什么错？谢谢，约翰
{_readableState: {…}, readable: true, domain: null, _events: {…}, _eventsCount: 0}
domain: null
readable: true
_events: {}
_eventsCount: 0
_readableState:
awaitDrain: 0
buffer:
head:
data:
data: (65) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 52, 51, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 98, 111, 98, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 51, 57, 56, 50, 49, 49, 48, 57, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 52, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 97, 108, 105, 99, 101, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 51, 57, 57, 48, 57, 48, 49, 51, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 53, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 99, 108, 105, 102, 102, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 52, 51, 54, 51, 56, 51, 52, 48, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 53, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 97, 114, 103, 101, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 52, 51, 55, 54, 53, 54, 48, 57, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 53, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 99, 108, 105, 110, 116, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 52, 51, 56, 49, 51, 49, 54, 55, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 54, 51, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 98, 121, 114, 111, 110, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 52, 51, 57, 52, 50, 48, 57, 54, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 54, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 105, 108, 116, 111, 110, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 52, 52, 50, 48, 55, 53, 52, 52, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 55, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 97, 114, 110, 111, 108, 100, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 52, 52, 52, 50, 51, 57, 55, 53, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 55, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 115, 97, 108, 108, 121, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 52, 56, 57, 56, 57, 52, 54, 57, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 57, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 97, 114, 118, 105, 110, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 53, 48, 51, 56, 50, 52, 54, 52, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 57, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 110, 97, 110, 99, 121, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 53, 48, 52, 49, 55, 52, 52, 57, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 52, 57, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 102, 114, 101, 100, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 53, 48, 52, 51, 48, 55, 52, 50, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 48, 51, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 97, 108, 101, 120, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 52, 53, 52, 56, 55, 57, 55, 53, 51, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 48, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 104, 101, 114, 109, 97, 110, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 53, 48, 54, 48, 50, 55, 50, 49, 55, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (69) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 49, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 97, 114, 103, 114, 101, 116, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 53, 53, 55, 53, 50, 49, 51, 55, 51, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (69) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 49, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 115, 121, 110, 116, 104, 105, 97, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 53, 53, 55, 53, 55, 51, 56, 52, 48, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 49, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 99, 111, 110, 110, 101, 114, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 53, 53, 55, 54, 48, 55, 51, 56, 55, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 50, 51, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 97, 114, 103, 111, 116, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 55, 53, 53, 56, 53, 57, 57, 50, 48, 48, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 50, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 100, 101, 110, 105, 115, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 48, 54, 54, 50, 56, 55, 53, 54, 48, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 51, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 112, 104, 105, 108, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 48, 54, 54, 56, 49, 50, 48, 55, 48, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 51, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 111, 114, 103, 97, 110, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 48, 55, 55, 53, 55, 55, 56, 53, 56, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 51, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 108, 117, 107, 101, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 48, 55, 50, 53, 48, 49, 51, 55, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 52, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 119, 97, 114, 114, 101, 110, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 48, 56, 52, 55, 50, 54, 56, 52, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 53, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 119, 105, 108, 98, 117, 114, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 49, 49, 49, 56, 54, 51, 55, 54, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 53, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 112, 97, 117, 108, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 49, 49, 50, 50, 52, 55, 57, 49, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (70) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 53, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 102, 108, 111, 114, 97, 110, 99, 101, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 53, 50, 50, 48, 48, 51, 50, 52, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (69) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 54, 51, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 117, 109, 102, 111, 114, 100, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 53, 50, 51, 55, 53, 57, 56, 50, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 54, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 98, 97, 114, 116, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 53, 55, 55, 48, 49, 57, 55, 49, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 55, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 104, 111, 109, 101, 114, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 53, 55, 55, 57, 48, 53, 49, 53, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (69) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 55, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 102, 97, 108, 107, 110, 101, 114, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 54, 51, 48, 52, 55, 52, 53, 52, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (70) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 55, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 97, 110, 100, 101, 114, 115, 111, 110, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 57, 54, 51, 56, 53, 50, 53, 51, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 56, 51, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 98, 97, 114, 114, 121, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 49, 57, 55, 55, 52, 54, 48, 55, 51, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 56, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 98, 97, 114, 110, 101, 121, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 50, 51, 54, 54, 52, 54, 54, 54, 50, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 57, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 98, 101, 116, 116, 121, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 50, 51, 54, 55, 52, 57, 54, 51, 54, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 57, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 115, 116, 101, 118, 101, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 50, 52, 52, 56, 49, 56, 48, 50, 52, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 53, 57, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 115, 104, 105, 114, 108, 121, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 50, 56, 49, 54, 49, 54, 50, 53, 52, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 48, 51, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 97, 103, 101, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 50, 56, 49, 56, 57, 54, 52, 50, 55, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (71) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 48, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 99, 111, 110, 115, 116, 97, 110, 99, 101, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 50, 48, 54, 56, 49, 53, 54, 54, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (68) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 49, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 109, 97, 114, 115, 104, 97, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 50, 48, 56, 55, 55, 57, 56, 54, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 49, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 103, 114, 101, 103, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 50, 49, 49, 53, 55, 49, 56, 53, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 50, 51, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 112, 101, 116, 101, 114, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 50, 49, 50, 48, 55, 55, 51, 55, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (67) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 50, 55, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 99, 105, 110, 100, 121, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 56, 52, 52, 52, 49, 52, 54, 49, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 51, 49, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 114, 111, 115, 101, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 56, 52, 52, 55, 50, 49, 48, 57, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (66) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 51, 53, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 98, 97, 114, 98, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 56, 52, 53, 51, 57, 52, 50, 52, 125, 10]
type: "Buffer"
__proto__: Object
next:
data:
data: (69) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 51, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 103, 105, 108, 98, 101, 114, 116, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 56, 52, 53, 57, 56, 56, 54, 55, 125, 10]
type: "Buffer"
__proto__: Object
next: null
length: 45
tail:
data:
data: (69) [123, 34, 117, 115, 101, 114, 73, 100, 34, 58, 54, 51, 57, 44, 34, 101, 109, 97, 105, 108, 34, 58, 34, 103, 105, 108, 98, 101, 114, 116, 64, 103, 109, 97, 105, 108, 46, 99, 111, 109, 34, 44, 34, 116, 105, 109, 101, 83, 116, 97, 109, 112, 34, 58, 49, 53, 54, 56, 52, 56, 52, 53, 57, 56, 56, 54, 55, 125, 10]
type: "Buffer"
__proto__: Object
next: null
I did not include the entire object.
如上所示，返回的对象中包含许多缓冲区。一世 认为每个缓冲区包含原始dbUsers中的一行/记录 删除了某些字段的文件，并删除了重复的记录。我会 希望将这些缓冲区视为人类可读的文本。因为很多 返回缓冲区，最终我将需要学习如何 遍历缓冲区，但现在我只是尝试打开 首先缓冲成文本。布拉德在这一点上处于不利地位 因为他不在电脑旁。所以他看不到我的代码 使用。无论如何，他都建议我尝试toString（） 功能。因此，我在第一个缓冲区上尝试了以下代码行。
console.log(value._readableState.buffer.head.data.data.toString());结果是以下数字。我希望有一串 文本。谁能看到我做不到的事情？谢谢，约翰
123,34,117,115,101,114,73,100,34,58,52,52,51,44,34,101,109,97,105,108,34,58,34,98,111,98,64,103,109,97,105,108,46,99,111,109,34,44,34,116,105,109,101,83,116,97,109,112,34,58,49,53,54,55,52,51,57,56,50,49,49,48,57,125,10
尝试以下代码行后，我仍然无法获得数字 控制台上的字母。
console.log(value._readableState.buffer.head.data.data.toString('utf8'));谢谢，约翰
答案 0 :(得分：1)
由于您使用的是Chrome，因此您可以在一个漂亮的管道中使用所有新功能，例如TextDecoderStream和TransformStream，该管道可以从HTTP响应中流式传输数据并对其进行行分隔的JSON解码。检查一下：
const fetchPromise = fetch(url, params).then((res) => {
// Verify that we have some sort of 2xx response that we can use
if (!res.ok) {
throw res;
}
// If no content, immediately resolve, don't try to parse JSON
if (res.status === 204) {
return;
}
let textBuffer = '';
const self = this;
return res.body
// Decode as UTF-8 Text
.pipeThrough(new TextDecoderStream())
// Split on lines
.pipeThrough(new TransformStream({
transform(chunk, controller) {
textBuffer += chunk;
const lines = textBuffer.split('\n');
for (const line of lines.slice(0, -1)) {
controller.enqueue(line);
}
textBuffer = lines.slice(-1)[0];
},
flush(controller) {
if (textBuffer) {
controller.enqueue(textBuffer);
}
}
}))
// Parse JSON objects
.pipeThrough(new TransformStream({
transform(line, controller) {
if (line) {
controller.enqueue(
JSON.parse(line)
);
}
}
}));
});
现在，您可以像使用其他任何对象一样使用此新对象流：
const res = await fetchPromise;
const reader = res.getReader();
function read() {
reader.read().then(({value, done}) => {
if (value) {
// Your object will be here
}
if (done) {
return;
}
read();
});
}
read();
（注意：我没有在此示例上下文中测试此代码...我从一个项目中对其进行了修改，因此请仔细研究并使其适合您的特定目的。）
答案 1 :(得分：0)
Brad的JavaScript在浏览器中运行正常。
问题是流从NodeJS服务器发送到浏览器的方式。
所有工作代码都已推送到github。
Click here to see the full repository which uses no dependencies.
The action starts here with the function called loadUsersListPage
为了方便起见，下面列出了该功能。
这是布拉德（Brad）的代码，该代码从服务器请求文本流，然后使用该流用服务器上dbUsers表中的用户列表填充网页。
// Populate the dbUsersList webpage with user records.
app.loadUsersListPage = async function()
{
// Create a handle which can be used to manipulate the table on the webpage.
var table = document.getElementById("usersListTable");
// Define which users will be retrieved from dbUsers.json
// This is not being used for now so all records will be retrived.
var QueryStringObject = {};
// Define a client function that calls for data from the server.
const fetchPromise = fetch('api/aUsers')
.then
(
(res) =>
{
// Verify that we have some sort of 2xx response that we can use
if (!res.ok)
{
// throw res;
// Show 'you have no checks' message
document.getElementById("noChecksMessage").style.display = 'table-row';
// Show the createCheck CTA
document.getElementById("createCheckCTA").style.display = 'block';
console.log("Error trying to load the list of users: ");
}
// If no content, immediately resolve, don't try to parse JSON
if (res.status === 204)
{
return;
}
// Initialize variable to hold chunks of data as they come across.
let textBuffer = '';
// Process the stream.
return res.body
// Decode as UTF-8 Text
.pipeThrough
(
new TextDecoderStream()
)
// Split on lines
.pipeThrough
(
new TransformStream
(
{
transform(chunk, controller)
{
textBuffer += chunk;
// Split the string of records on the new line character and store the result in an array named lines.
const lines = textBuffer.split('\n');
// Cycle through all elements in the array except for the last one which is only holding a new line character.
for (const line of lines.slice(0, -1))
{
// Put the element from the array into the controller que.
controller.enqueue(line);
} // End of: for (const line ...)
// Put the last element from the array (the new line character) into the textBuffer but don't put it in the que.
textBuffer = lines.slice(-1)[0];
}, // End of: Transform(chunk, controller){do stuff}
flush(controller)
{
if (textBuffer)
{
controller.enqueue(textBuffer);
} // End of: if (textBuffer)
} // End of: flush(controller){do stuff}
} // End of: parameters for new TransformStream
) // End of: call to constructor new TransformStream
) // End of: parameters for pipeThrough - Split on lines
// Parse JSON objects
.pipeThrough
(
new TransformStream
(
{
transform(line, controller)
{
if (line)
{
controller.enqueue
(
JSON.parse(line)
); //End of: call to controller.enqueue function
} // End of: if (line)
} // End of: transform function
} // End of: parameter object for new TransformStream
) // End of: new TransformStream parameters
); // End of: parameters for .pipeThrough - Parse JSON objects
} // End of: .then callback function instruction for fetch
); // End of: .then callback parameters for fetch
// Call to function which asks server for data.
const res = await fetchPromise;
const reader = res.getReader();
function read()
{
reader.read()
.then
(
({value, done}) =>
{
if (value)
{
// Your object (value) will be here
// Insert a new row in the table.
var tr = table.insertRow(-1);
// Make the new row a member of the class 'checkRow'
tr.classList.add('checkRow');
// Insert five new cells into the new row.
var td0 = tr.insertCell(0);
var td1 = tr.insertCell(1);
var td2 = tr.insertCell(2);
var td3 = tr.insertCell(3);
// load the new cells with data from the recordObject.
td0.innerHTML = value.userId;
td1.innerHTML = value.email;
td2.innerHTML = value.timeStamp;
td3.innerHTML = '<a href="/users/edit?email=' + value.userId + '">View / Edit / Delete</a>';
} // End of: if(value){do stuff}
if (done) {return;}
read();
// Show the createCheck CTA
document.getElementById("createCheckCTA").style.display = 'block';
} // End of: if a record object (value) is returned.
); // End of: .then callback after read function completes.
} // End of: function definition: function read(){do stuff}
// Call the read function defined above.
read();
} // End of: app.loadUsersListPage = function(){...}
// End of: Populate the dbUsersList webpage with user records.
The working server code is found here under the function named unifiedServer
为了方便起见，该功能在下面直接列出。
此函数将请求路由到处理程序（也在下面列出），然后发送 返回数据流返回到浏览器，以获取Brad的代码 食用。
在函数底部附近，您可以看到用于将流发送到浏览器的管道。
这就是我所缺少的。
// Define a function to route requests from the client to the handler and to serve back a response.
// All the logic for both the http and https server
server.unifiedServer = function(req, res)
{
// Get the URL and parse it.
var parsedUrl = url.parse(req.url, true);
// Get the path from the URL.
var path = parsedUrl.pathname;
var trimmedPath = path.replace(/^\/+|\/+$/g, '');
// Get the query string as an object.
var queryStringObject = parsedUrl.query;
// Get the http method.
var method = req.method.toLowerCase();
// Get the headers as an Object
var headers = req.headers;
// Instantiate decoder that will turn payload buffer into a string.
var decoder = new StringDecoder('utf8');
// Create an empty string for the request payload.
// It's called buffer but it is not a JavaScript buffer (not binary data) - it's just an empty string.
// We are going to use it to hold the request payload buffer after it has been decoded and turned into a string.
var buffer = '';
// Call to event emitter req.on('data...
// Watch for a chunk of data from the client's request payload buffer.
// The run the callback defined below with the returned data.
req.on('data', function(data)
{
// Decode the chunk and write it to the payload string.
buffer += decoder.write(data);
});
// Call to event emitter req.on('end...
// Watch for the end of the payload from the client request.
// The callback defined here is the action taken after the entire request has been received.
req.on('end', function()
{
// Finish writing to the buffer.
buffer += decoder.end();
// Choose the handler the client's request should go to.
// If one is not found, use the notFound handler.
// To be clear: A key in the router object below should match the request from the client.
// chosenHandler becomes an alias for the handler function which is mapped to the key in the router object.
// This is how we can refer to the handler function without knowing what it is in advance.
var chosenHandler = typeof(server.router[trimmedPath]) !== 'undefined' ? server.router[trimmedPath] : aHandlers.notFound;
// If the request is within the public directory, use the public handler instead of what was assigned by the line above.
// The line below is required because the line above will only match a handler to a client request if
// the request exactly matches one of the keys in the request router object at the bottom of this file.
// So if the request is "public" then we have a match with the public handler. But request
// public/app.css would not be matched with a handler.
chosenHandler = trimmedPath.indexOf('public/') > -1 ? handlers.public : chosenHandler;
// Construct the data object to send to the handler.
var data =
{
'trimmedPath' : trimmedPath,
'queryStringObject' : queryStringObject,
'method' : method,
'headers' : headers,
'payload' : aHelpers.parseJsonToObject(buffer)
}; // End of: Construct the data object to send to the handler.
// Call the handler specified by the client.
// Then execute the callback we are passing in as an argument.
chosenHandler(data, function(statusCode, payload, contentType)
{
// Determine the type of response - default to json.
contentType = typeof(contentType) == 'string' ? contentType : 'json';
// Use the status code called back by the handler, or default to 200.
statusCode = typeof(statusCode) == 'number' ? statusCode : 200;
// Return the response parts that are content specific.
var payloadString = '';
if(contentType == 'json')
{
res.setHeader('Content-Type', 'application/json');
// Use the payload called back by the handler, or default to an empty object.
payload = typeof(payload) =='object' ? payload : {};
// Convert the payload to a string.
payloadString = JSON.stringify(payload);
}
if(contentType == 'html')
{
res.setHeader('Content-Type', 'text/html');
payloadString = typeof(payload) == 'string' ? payload : '';
}
if(contentType == 'favicon')
{
res.setHeader('Content-Type', 'image/x-icon');
payloadString = typeof(payload) !== 'undefined' ? payload : '';
}
if(contentType == 'css')
{
res.setHeader('Content-Type', 'text/css');
payloadString = typeof(payload) !== 'undefined' ? payload : '';
}
if(contentType == 'png')
{
res.setHeader('Content-Type', 'image/png');
payloadString = typeof(payload) !== 'undefined' ? payload : '';
}
if(contentType == 'jpg')
{
res.setHeader('Content-Type', 'image/jpeg');
payloadString = typeof(payload) !== 'undefined' ? payload : '';
}
if(contentType == 'plain')
{
res.setHeader('Content-Type', 'text/plain');
payloadString = typeof(payload) !== 'undefined' ? payload : '';
}
// Return the response parts that are common to all content-types.
res.writeHead(statusCode);
if (contentType == 'stream')
{
pipeline
(
payload,
res,
function(error){if(error){console.log('There was an error.');}}
);
}
else
{
res.end(payloadString);
}
console.log('Returning this response: ', statusCode);
}); // End of: call to chosenHandler(...
}); // End of: call to req.on('end', function(...
}; // End of: var unifiedServer = function(...
// End of: Define a function to route requests from the client to the handler and to serve back a response.
处理程序函数，其中：
从dbUsers.json文件读取数据，
处理数据，
并将其作为流返回
can be found here under the name handlers._users.get
为了方便起见，下面列出了该功能。
handlers._users.get = function(data, callback)
{
// Create an empty map data structure which will be used to merge user records with the same email address.
let usersMap = new Map();
// This function sets up a stream where each chunk of data is a complete line in the dbUsers file.
let readInterface = readline.createInterface
(
{ // specify the file to be read.
input: fs.createReadStream(_data.baseDir + '/dbPermissions/dbUsers' + '/' + 'dbUsers' + '.json'),
}
);
// Look at each record in the file.
readInterface.on('line', function(line)
{
// Convert the JSON string (a single line from the dbUsers file) into lineValueObject.
// These objects will written back to a new file after deleting some un-needed key/value pairs.
let lineValueObject = JSON.parse(line);
// Declare a variable to serve as a key in the map to manage the lineValueObject.
let userId = lineValueObject.userId;
if(lineValueObject.deleted === true)
{
// Remove this record from the map
usersMap.delete(userId);
}
else // this record has not been marked for deletion.
{
// Remove the hashed password key/value pair from the lineValueObject before returning it to the requester.
delete lineValueObject.hashedPassword;
// Remove the deleted key/value pair from the lineValueObject before returning it to the requester.
delete lineValueObject.deleted;
// Update this record in the map.
usersMap.set(userId, lineValueObject);
}
}); // End of: readInterface.on('line', function(line){...}
// End of: Look at each record...
// This listener fires after we have looked through all the records in the dbUsers file.
// The callback function defined here will stream the list of users back to the clients browser.
readInterface.on('close', function()
{
// This readable stream will be used to write the result of the merge to a new file.
const sourceStream = new Readable();
for (const [key, valueObject] of usersMap)
{
// Convert the data object to a string.
let stringData = JSON.stringify(valueObject);
// Load the readable stream with data.
sourceStream.push(stringData + '\n');
}
// Tell the stream no more data is coming.
sourceStream.push(null);
callback(200, sourceStream, 'stream');
}); // End of: readInterface.on('close', function(){...}
}; // End of: handlers._users.get = function(data, callback){do stuff}