我想在现有的csv文件中添加新行?如果存在csv文件,那么我不想添加列标题,只想在文件中存在行之后添加新行。
以下是我正在尝试的代码:
var fields = ['total', 'results[0].name.val'];
var fieldNames = ['Total', 'Name'];
var opts1 = {
data: data,
fields: fields,
fieldNames: fieldNames,
newLine: '\r\n'
};
var opts2 = {
newLine: '\r\n',
data: data,
fields: fields,
fieldNames: fieldNames,
hasCSVColumnTitle: false,
};
fs.stat('file.csv', function (err, stat) {
if (err == null) {
console.log('File exists');
var csv = json2csv(opts2);
fs.appendFile('file.csv', csv, function (err) {
if (err) throw err;
console.log('The "data to append" was appended to file!');
});
} else if (err.code == 'ENOENT') {
// file does not exist
var csv = json2csv(opts1);
fs.writeFile('file.csv', csv, function (err) {
if (err) throw err;
console.log('file saved');
});
} else {
console.log('Some other error: ', err.code);
}
});
答案 0 :(得分:10)
以下代码将按您的要求执行:
之后的每次运行 - 将json数据附加到csv文件
var fs = require('fs');
var json2csv = require('json2csv');
var newLine= "\r\n";
var fields = ['Total', 'Name'];
var appendThis = [
{
'Total': '100',
'Name': 'myName1'
},
{
'Total': '200',
'Name': 'myName2'
}
];
var toCsv = {
data: appendThis,
fields: fields,
hasCSVColumnTitle: false
};
fs.stat('file.csv', function (err, stat) {
if (err == null) {
console.log('File exists');
//write the actual data and end with newline
var csv = json2csv(toCsv) + newLine;
fs.appendFile('file.csv', csv, function (err) {
if (err) throw err;
console.log('The "data to append" was appended to file!');
});
}
else {
//write the headers and newline
console.log('New file, just writing headers');
fields= (fields + newLine);
fs.writeFile('file.csv', fields, function (err, stat) {
if (err) throw err;
console.log('file saved');
});
}
});
答案 1 :(得分:2)
我对函数的行为进行了一些更改,现在我用2种方法验证是否有标题,如果存在,我将忽略它并添加行,如果没有,则添加标题,从对象中删除引号并传递一些等待,因为该函数是同步的,没有等待,所以异步是没有意义的哈哈哈
传递给filename的CSV值是节点将在项目根目录中查找以保存最终文档的文件夹的名称
??
Fiz umasmudançasem como afunçãose comporta,agora eu valido com 2个存在的cabeçalho,这些存在的euignoro ele e adiciono成行,senãoeu adiciono ocabeçalho,移除aspas dos objetos porque afunçãoage sync enãotinha nenhum awaitentãonãofazia sentido ser async hahaha
Oval CSV passado参数或命令的最终面目是什么?
const fs = require("fs");
const path = require("path");
const json2csv = require("json2csv").parse;
// Constructor method to assist our ReadFileSync
const readFileSync = filePath =>
fs.readFileSync(filePath, { encoding: "utf-8" });
// A helper to search for values in files =D
const findWord = async (text, filePath) => {
const result = await readFileSync(path.join(__dirname, filePath));
return Promise.resolve(RegExp("\\b" + text + "\\b").test(result));
};
const write = async (fileName, fields, data) => {
// output file in the same folder
const filename = path.join(__dirname, "CSV", `${fileName}`);
let rows;
// I check if there is a header with these items
const hasValue = await findWord("Name,Position,Salary", "./CSV/test.csv");
// If there is a header I add the other lines without it if I don't follow the natural flow
if (hasValue) {
rows = json2csv(data, { header: false });
} else if (!fs.existsSync(fields)) {
// If file doesn't exist, we will create new file and add rows with headers.
rows = json2csv(data, { header: true });
} else {
// Rows without headers.
rows = json2csv(data, { header: false });
}
// I deal with the information by removing the quotes
const newRows = rows.replace(/[\\"]/g, "");
// Append file function can create new file too.
await fs.appendFileSync(filename, newRows);
// Always add new line if file already exists.
await fs.appendFileSync(filename, "\r\n");
};
fields = ["Name", "Position", "Salary"];
data = [
{
Name: "Test1",
Position: "Manager",
Salary: "$10500",
},
{
Name: "Test2",
Position: "Tester",
Salary: "$5500",
},
{
Name: "Test3",
Position: "Developer",
Salary: "$5500",
},
{
Name: "Test4",
Position: "Team Lead",
Salary: "$7500",
},
];
write("test.csv", fields, data);
Output:
"Name","Position","Salary"
"Test1","Manager","$10500"
"Test2","Tester","$5500"
"Test3","Developer","$5500"
"Test4","Team Lead","$7500"
答案 2 :(得分:1)
使用csv-write-stream函数将数据附加到csv文件中。
https://www.npmjs.com/package/csv-write-stream 添加带有标志“ a”的行
writer.pipe(fs.createWriteStream('out.csv',{flags:'a'}))
答案 3 :(得分:0)
使用json-2-csv:
/**
* this function will create the file if not exists or append the
* data if exists
*/
function exportToCsvFile(headersArray, dataJsonArray, filename) {
converter.json2csvAsync(dataJsonArray, {prependHeader: false}).then(function (csv) {
fs.exists(filename + '.csv', async function (exists) {
if (!exists) {
var newLine = "\r\n";
var headers = ((headersArray ? headersArray : []) + newLine);
exists= await createFileAsync(filename+ '.csv', headers);
}
if (exists) {
fs.appendFile(filename + '.csv', csv, 'utf8', function (err) {
if (err) {
console.log('error csv file either not saved or corrupted file saved.');
} else {
console.log(filename + '.csv file appended successfully!');
}
});
}
});
}).catch(function (err) {
console.log("error while converting from json to csv: " + err);
return false;
});
}
function createFileAsync(filename, content) {
return new Promise(function (resolve, reject) {
fs.writeFile(filename, content, 'utf8', function (err) {
if (err) {
console.log('error '+filename +' file either not saved or corrupted file saved.');
resolve(0);
} else {
console.log(filename + ' file created successfully!');
resolve(1);
}
});
});
}
答案 4 :(得分:0)
似乎,json2csv
的最新版本具有称为.parse()
的专用方法,可以将JSON转换为CSV兼容字符串。我尝试了json2csv.parse()
转换器,它对我有用。
我在此处给出的解决方案中发现了一个常见问题。如果我们多次运行该方法,则解决方案不会在没有HEADER
的情况下追加数据。
我使用了header
提供的json2csv
布尔选项来解决此问题。如果我们使用{header:false}
选项进行解析,我们将获得数据作为行。
// Rows without headers.
rows = json2csv(data, { header: false });
下面是我上面提到的完全有效的代码:
下面是代码示例:
const fs = require('fs');
const path = require('path');
const json2csv = require('json2csv').parse;
const write = async (fileName, fields, data) => {
// output file in the same folder
const filename = path.join(__dirname, 'CSV', `${fileName}`);
let rows;
// If file doesn't exist, we will create new file and add rows with headers.
if (!fs.existsSync(filename)) {
rows = json2csv(data, { header: true });
} else {
// Rows without headers.
rows = json2csv(data, { header: false });
}
// Append file function can create new file too.
fs.appendFileSync(filename, rows);
// Always add new line if file already exists.
fs.appendFileSync(filename, "\r\n");
}
Write
函数我们有3个参数:
fields = ['Name', 'Position', 'Salary'];
data = [{
'Name': 'Test1',
'Position': 'Manager',
'Salary': '$10500'
},
{
'Name': 'Test2',
'Position': 'Tester',
'Salary': '$5500'
}, {
'Name': 'Test3',
'Position': 'Developer',
'Salary': '$5500'
}, {
'Name': 'Test4',
'Position': 'Team Lead',
'Salary': '$7500'
}];
现在调用函数write
:
write('test.csv', fields, data);
每次我们调用上述方法时,它都会从新行开始写入。如果文件不存在,它将只写入一次标头。