我是javaScript的新手，正在尝试将CSV或TXT文件加载到浏览器中。
当选择文件时，事件处理程序显示文件名和详细信息，一旦用户点击加载按钮，脚本应该仔细检查文件扩展名，加载文件然后对文件进行一些进一步的检查。
我的问题是文件加载函数似乎总是被调用，这意味着其他检查首先发生。
该文件保存在此处：http://bananamountain.net/project/20140703pm/file-loader2.html
下面粘贴的代码：
</head>
<body>
<script>
// Check for the various File API support.
if (window.File && window.FileReader && window.FileList && window.Blob) {
// Great success! All the File APIs are supported.
} else {
alert('The File APIs are not fully supported in this browser.');
}
</script>
<h3>File Load test</h3>
<p>Use only test-data-csv.csv just now</p>
<input type="file" id="file" name="file" required="required" accept=".csv, .txt" />
<button onclick="handleFileLoad()">Load button</button>
<output id="list"></output>
<script>
// global variables
var content;
var fileName;
var splitString = ",";
var rows = new Array();
var headerRow = new Array();
var values = new Array();
function handleFileLoad() {
//var suitableFileType = checkFileType();
//document.write("<strong>Suitable file type: " + suitableFileType + "</strong><br />");
loadFile();
var suitableContent = checkFileContent();
document.write("<strong>Suitable file content: " + suitableContent + "</strong><br />");
}
function checkFileType() {
document.write("inside checkFileType<br/>");
// var testFile = fileName.split(".")[1].toUpperCase();
// document.write("file extension is '" + testFile+ "'<br />");
if ((fileName.split(".")[1].toUpperCase() === "CSV")) {
document.write('suitable file selected<br/>');
return (true);
} else if (fileName.split(".")[1].toUpperCase() === "TXT") {
document.write('suitable file selected<br/>');
return (true);
}else {
document.write('Invalid file format! \nPlease select a suitable .txt or .csv file<br/>');
return (false);
}
} // end of checkFileType - tested WORKING
function loadFile() {
// checkFileType();
var file = document.getElementById("file").files[0];
var reader = new FileReader();
var link_reg = /(http:\/\/|https:\/\/)/i;
reader.onload = function(file) {
// content = reader.result;
content = file.target.result;
rows = file.target.result.split(/[\r\n|\n]+/);
for (var i=0; i<rows.length; i++) {
document.write("row found at line " + i + " is " + rows[i] +".<br/>");
}
};
reader.readAsText(file);
/*
var suitableFileType = checkFileType();
document.write("<strong>Suitable file type: " + suitableFileType + "</strong><br />");
var suitableContent = checkFileContent();
document.write("<strong>Suitable file content: " + suitableContent + "</strong><br />");
var splitStringFound = getSplitString();
document.write("<strong>Split string found: " + splitStringFound + "</strong><br />");
document.write("<strong>Split String: " + splitString + "</strong><br/>");
var replacedHeaders = checkHeaderRow();
document.write("<strong>Header row complete<br />" + replacedHeaders +" headers replaced</strong><br/>");
document.write(content);
document.write(fileName);
document.write(splitString);
document.write(rows);
document.write( headerRow);
document.write(values);*/
return;
}
function checkFileContent() {
document.write("inside check file content<br/>");
// check for file content
// identifies blank lines and deletes them
// checking content of rows
for (var i=0;i<rows.length;i++) {
document.write ("Row " + i + " is " + rows[i]);
}
var filteredArr = rows.filter(function (val) {
return !(val === "" || typeof val == "undefined" || val === null || val === ",," || val === "\t\t");
});
// identifies empty file (e.g. all blank lines deleted)
if (filteredArr.length === 0) {
document.write("Empty file - no data found <br/>");
rows = filteredArr;
return false;
// check for row deletions
} else if (rows.length < filteredArr.length) {
rows = filteredArr;
document.write("blank rows deleted - " + (rows.length - filteredArr.length) + " rows remaining. <br/>");
return ("deletions");
} else {
document.write("No blank rows <br/>");
return true;
}
} // end of check file content - empty file tested, file with one line tested
function checkHeaderRow() {
// check for header row
// words in first non-empty row
var replaceCount = 0;
var checkArray = rows[0].split(splitString);
for (var i = 1; i < checkArray.length; i++) {
// start at array[1] as array[0] not likely to be a header value
// loop through inserting non numeric values into headerRow array
if (isNaN(checkArray[i])) {
headerRow[i - 1] = checkArray[i];
// need a flag to remove this from file once it has been done
replaceCount++;
} else {
headerRow[i - 1] = "Risk " + i;
}
}
// if non numeric values in array[1] delete rows[0]
// so the header row is not included with the data set
if (isNaN(checkArray[1])) {
rows[0] = null;
}
return (replaceCount);
} // end of checkHeaderRow works for all non-numeric, all numeric and mixed
function getSplitString() {
// call countCharacter to return count of comma and tab characters in first five lines
var tabCount = countCharacter("\t");
var commaCount = countCharacter(",");
// compare tabCount and commaCount values
if (tabCount === 0 && commaCount === 0) {
document.write("Cannot detect the value seperator,\n please ammend file to seperate values with tabs or commas");
return false;
}
else if (tabCount === commaCount) {
splitString = prompt("Cannot detect the value seperator,\n please input \"\\t\" for tabs or \",\" for commas");
if ((splitString === null) || (splitString != '\t') || (splitString != ',')) {
document.write("please check file and try again<br/>");
splitString = ',';
return false;
} // NOT WORKING
else {
return true;
}
} else if (tabCount>commaCount) {
splitString = "\t";
if (commaCount!=0) {
document.write("tab character selected as value seperator.<br/>");
// alert as this may not be the case
}
return true;
} else {
splitString=",";
if (tabCount!=0){
document.write("tab character selected as value seperator.<br/>");
// alert as this may not be the case
}
return true;
}
} // end of getSplitString - NOT FULLY WORKING
function splitRows() {
// what if rows is now empty? (e.g. header row only in file)
if (rows[0] != null) {
for (var i=0; i<rows.length;i++) {
values.push(rows[i].split(splitString));
}
return values;
} else {
return false;
}
} // end of splitRows fully working
function checkEmptyCells () {
for (var i=0; i<values.length; i++) {
for (var j=0; j<values[i].length; j++)
if (!((values[i][j] === "") || (typeof values[i][j] == "undefined") || (values[i][j] === null) || (values[i][j] === ",,") || (values[i][j] === "\t\t"))) {
// remove line values[i][j]
document.write("in here");
}
}
} // NOT FININSHED - STOPPED HERE
function countCharacter (character) {
// count the instances of a specified character over first 5 lines (or length of rows array)
// number of rows to loop through
var loopCount=0;
var characterCount=0;
if (rows.length < 5) {
loopCount = rows.length;
} else {
loopCount = 5;
}
for (var count=0; count < loopCount; count++) {
characterCount += rows[count].split(character).length-1;
}
return characterCount;
} // End of countCharacter - WORKING - TESTED
function handleFileSelect(evt) {
var files = evt.target.files; // FileList object
// files is a FileList of File objects. List some properties.
var output = [];
for (var i = 0, f; f = files[i]; i++) { // THIS IS NOT NEEDING TO BE IN A LOOP
output.push('<strong>', escape(f.name), '</strong> ', ' - ',
f.size, ' bytes, last modified: ',
f.lastModifiedDate ? f.lastModifiedDate.toLocaleDateString() : 'n/a',
'');
fileName = escape(f.name);
}
document.getElementById('list').innerHTML = '<div class="file-name">' + output.join('') + '</div>';
}
document.getElementById('file').addEventListener('change', handleFileSelect, false);
</script>
</body>
</html>
答案 0 :(得分：0)
首先，我认为我提出的问题是错误的，正是由于这个原因，答案有限。我添加了答案，以便如果有人遇到同样的问题，并且遇到这个问题就可以帮助他们。
问题不在于加载html文件，而是通过javascript加载文件。该脚本对文件进行了一些检查，加载了文件，然后对文件内容进行了进一步的检查。
这一切都正确发生，但javascript做了一个叫做asyncronious加载的东西，它依次调用函数，但在当前函数完成它正在做的事情之前移动到下一个函数。
想象一下，你去酒吧，订购饮料，支付饮料，然后去你的餐桌。 Javascript可以做到这一点，但没有等待获得服务的正常停顿，饮料的使用和变化。
基本上我的代码是在没有饮料的情况下回到表中（或者在没有完成加载的情况下检查文件的内容）。
为了解决这个问题，我花了一些时间，这可能并不是最好的，因为加载速度将取决于文件的大小。然而，它现在适用，并允许我继续其他的东西。
工作代码的片段如下： { function handleFileLoad（）{
if (checkFileType()) {
values = [];
loadFile();
} else {
alert("Invalid file format! \nPlease select a suitable .txt or .csv file<br/>");
return;
}
//setTimeout(fileContentChecks(), 1000);
if (!setTimeout(fileContentChecks(), 1000)) {
return;
} else {
setData(); //PROBABLY PUT THESE IN A FUNCTION OR TWO
setComboLists(); //SO THESE CAN BE CALLED LATER TO UPDATE PAGE
UpdateAssetList();
UpdateXAxisList();
UpdateYAxisList();
UpdateTable();
}
}
function checkFileType() { // CHECK FILE NAME EXTENSION
if ((fileName.split(".")[1].toUpperCase() === "CSV")) {
return (true);
} else if (fileName.split(".")[1].toUpperCase() === "TXT") {
return (true);
} else {
return (false);
}
} // end of checkFileType - tested WORKING
function loadFile() { // LOADS FILE AND SPLITS INTO ROWS
var file = document.getElementById("file").files[0];
var reader = new FileReader();
var link_reg = /(http:\/\/|https:\/\/)/i;
reader.onload = function(file) {
content = file.target.result;
rows = file.target.result.split(/[\r\n|\n]+/);
};
reader.readAsText(file);
// NEEDS TIMEOUT HERE.....
return;
} // end of loadFile - TESTED WORKS WHEN STEPPING THROUGH - NEEDS TIMEOUT
function fileContentChecks() {
if (checkFileContent()) {
if (getSplitString()) {
checkHeaderRow();
} else {
alert("Seperator value not found"); // not sure if this is required?
return false;
}
} else {
alert("File contents not verified, please check file and try again.");
return false;
}