[nodejs]按行读取文本文件

原文：https://segmentfault.com/a/1190000000740718

var stream = require('stream')
var liner = new stream.Transform( { objectMode: true } )

liner._transform = function (chunk, encoding, done) {
  var data = chunk.toString()
  if (this._lastLineData) data = this._lastLineData + data

  var lines = data.split('\n')
  this._lastLineData = lines.splice(lines.length-1,1)[0]

  lines.forEach(this.push.bind(this))
  done()
}

liner._flush = function (done) {
     if (this._lastLineData) this.push(this._lastLineData)
     this._lastLineData = null
     done()
}

module.exports = liner

//测试：打印出文本文件的每一行
var fs = require('fs')
var source = fs.createReadStream('aaa.txt')
source.pipe(liner)
liner.on('readable', function () {
  var line
  while (line = liner.read()) {
    console.log(line);
  }
})