我用这个:

function emitLines(stream, re){
    re = re && /\n/;
    var buffer = '';

    stream.on('data', stream_data);
    stream.on('end', stream_end);

    function stream_data(data){
        buffer += data;
        flush();
    }//stream_data

    function stream_end(){
        if(buffer) stream.emmit('line', buffer);
    }//stream_end


    function flush(){
        var re = /\n/;
        var match;
        while(match = re.exec(buffer)){
            var index = match.index + match[0].length;
            stream.emit('line', buffer.substring(0, index));
            buffer = buffer.substring(index);
            re.lastIndex = 0;
        }
    }//flush

}//emitLines

在流上使用此函数并侦听将发出的行事件。

gr-

从Node.js v0.12和Node.js v4.0.0开始，有一个稳定的readline核心模块。下面是从文件中读取行，不需要任何外部模块的最简单方法:

const fs = require('fs');
const readline = require('readline');

async function processLineByLine() {
  const fileStream = fs.createReadStream('input.txt');

  const rl = readline.createInterface({
    input: fileStream,
    crlfDelay: Infinity
  });
  // Note: we use the crlfDelay option to recognize all instances of CR LF
  // ('\r\n') in input.txt as a single line break.

  for await (const line of rl) {
    // Each line in input.txt will be successively available here as `line`.
    console.log(`Line from file: ${line}`);
  }
}

processLineByLine();

或者:

var lineReader = require('readline').createInterface({
  input: require('fs').createReadStream('file.in')
});

lineReader.on('line', function (line) {
  console.log('Line from file:', line);
});

最后一行被正确读取(截至Node v0.12或更高版本)，即使没有最后的\n。

更新:此示例已添加到Node的API官方文档中。

function createLineReader(fileName){
    var EM = require("events").EventEmitter
    var ev = new EM()
    var stream = require("fs").createReadStream(fileName)
    var remainder = null;
    stream.on("data",function(data){
        if(remainder != null){//append newly received data chunk
            var tmp = new Buffer(remainder.length+data.length)
            remainder.copy(tmp)
            data.copy(tmp,remainder.length)
            data = tmp;
        }
        var start = 0;
        for(var i=0; i<data.length; i++){
            if(data[i] == 10){ //\n new line
                var line = data.slice(start,i)
                ev.emit("line", line)
                start = i+1;
            }
        }
        if(start<data.length){
            remainder = data.slice(start);
        }else{
            remainder = null;
        }
    })

    stream.on("end",function(){
        if(null!=remainder) ev.emit("line",remainder)
    })

    return ev
}


//---------main---------------
fileName = process.argv[2]

lineReader = createLineReader(fileName)
lineReader.on("line",function(line){
    console.log(line.toString())
    //console.log("++++++++++++++++++++")
})

我使用下面的代码读取行后，验证它不是一个目录，它不包括在文件列表不需要检查。

(function () {
  var fs = require('fs');
  var glob = require('glob-fs')();
  var path = require('path');
  var result = 0;
  var exclude = ['LICENSE',
    path.join('e2e', 'util', 'db-ca', 'someother-file'),
    path.join('src', 'favicon.ico')];
  var files = [];
  files = glob.readdirSync('**');

  var allFiles = [];

  var patternString = [
    'trade',
    'order',
    'market',
    'securities'
  ];

  files.map((file) => {
    try {
      if (!fs.lstatSync(file).isDirectory() && exclude.indexOf(file) === -1) {
        fs.readFileSync(file).toString().split(/\r?\n/).forEach(function(line){
          patternString.map((pattern) => {
            if (line.indexOf(pattern) !== -1) {
              console.log(file + ' contain `' + pattern + '` in in line "' + line +'";');
              result = 1;
            }
          });
        });
      }
    } catch (e) {
      console.log('Error:', e.stack);
    }
  });
  process.exit(result);

})();

另一个解决方案是通过顺序执行器nsynjs运行逻辑。它使用节点readline模块逐行读取文件，并且不使用承诺或递归，因此在大文件上不会失败。下面是代码的样子:

var nsynjs = require('nsynjs');
var textFile = require('./wrappers/nodeReadline').textFile; // this file is part of nsynjs

function process(textFile) {

    var fh = new textFile();
    fh.open('path/to/file');
    var s;
    while (typeof(s = fh.readLine(nsynjsCtx).data) != 'undefined')
        console.log(s);
    fh.close();
}

var ctx = nsynjs.run(process,{},textFile,function () {
    console.log('done');
});

上面的代码基于这个示例:https://github.com/amaksr/nsynjs/blob/master/examples/node-readline/index.js

这是我最喜欢的浏览文件的方式，是使用现代async/await进行渐进式(不是“slurp”或全内存方式)文件读取的简单本机解决方案。在处理大型文本文件时，我发现这是一种“自然”的解决方案，而不必求助于readline包或任何非核心依赖项。

let buf = '';
for await ( const chunk of fs.createReadStream('myfile') ) {
    const lines = buf.concat(chunk).split(/\r?\n/);
    buf = lines.pop();
    for( const line of lines ) {
        console.log(line);
    }
}
if(buf.length) console.log(buf);  // last line, if file does not end with newline

您可以在fs中调整编码。creatererestream或使用chunk.toString(<arg>)。这也让你更好地微调线分裂到你的口味，即。使用.split(/\n+/)跳过空行，用{highWaterMark: <chunkSize>}控制块大小。

Don't forget to create a function like processLine(line) to avoid repeating the line processing code twice due to the ending buf leftover. Unfortunately, the ReadStream instance does not update its end-of-file flags in this setup, so there's no way, afaik, to detect within the loop that we're in the last iteration without some more verbose tricks like comparing the file size from a fs.Stats() with .bytesRead. Hence the final buf processing solution, unless you're absolutely sure your file ends with a newline \n, in which case the for await loop should suffice.

★如果你更喜欢事件异步版本，这将是它:

let buf = '';
fs.createReadStream('myfile')
.on('data', chunk => {
    const lines = buf.concat(chunk).split(/\r?\n/);
    buf = lines.pop();
    for( const line of lines ) {
        console.log(line);
    }
})
.on('end', () => buf.length && console.log(buf) );

★现在如果你不介意导入流核心包，那么这是等效的管道流版本，它允许链接转换，如gzip解压:

const { Writable } = require('stream');
let buf = '';
fs.createReadStream('myfile').pipe(
    new Writable({
        write: (chunk, enc, next) => {
            const lines = buf.concat(chunk).split(/\r?\n/);
            buf = lines.pop();
            for (const line of lines) {
                console.log(line);
            }
            next();
        }
    })
).on('finish', () => buf.length && console.log(buf) );