【逐日一包0021】csv2,through2

[github地点：https://github.com/ABCDdouyae&＃8230;]

csv2

采纳流形式读取.csv文件，每次读取一行数据

through2

对node流的二次封装，越发易于运用

一般用法 through2([ options, ] [ transformFunction ] [, flushFunction ])

• options：{objectMode: true} 等同于through2.obj
• transformFunction(chunk, encode, callback)
• flushFunction 能够使2号或许3号参数 每次撒布完能够和transformFunction一样做一些数据处置惩罚

//将文件中的a悉数替换为z输出到out.txt
const through2 = require('through2');
const fs = require('fs');
fs.createReadStream('./test/enter.txt')
.pipe(through2(function (chunk, enc, callback) {
for (var i = 0; i if (chunk[i] == 97)
chunk[i] = 122 // swap 'a' for 'z'
this.push(chunk)
callback()
}))
.pipe(fs.createWriteStream('./test/out.txt'))
.on('finish', () => {
console.log('完事')
})

through2.obj

const through2 = require('through2');
const csv2 = require('csv2');
const fs = require('fs');
let all = [];
fs.createReadStream('./test/enter.csv')
.pipe(csv2())
.pipe(through2.obj(function (chunk, enc, callback) {
this.push({
No : chunk[0],
activity : chunk[1],
time : chunk[2],
money: chunk[3]
})
callback()
}))
.on('data', (data)=>{
all.push(data)
})
.on('end', ()=>{
fs.writeFile('./test/a.js', JSON.stringify(all), ()=>{
console.log('写入完成')
})
})

through2.ctor关于须要雷同处置惩罚历程的数据能够采纳该要领建立一个组织函数

let Fc = through2.ctor(function(chunk, enc, callback){
console.log(chunk)
for(var i=0;i if(chunk[i]<=97){
chunk[i] = 98;
}
}
console.log(chunk);
this.push(chunk);
callback();
})
fs.createReadStream('./test/enter.txt')
.pipe(Fc())
.pipe(fs.createWriteStream('./test/out1.txt'))
.on('finish', () => {
console.log('完事')
})