如果要编写同步代码，请仅使用同步功能：
var fs = require("fs");fs.readFileSync('./input.txt').toString().split('n').forEach(function (line) { console.log(line); fs.appendFileSync("./output.txt", line.toString() + "n");});对于异步方法，您可以编写类似
var fs = require('fs'), async = require('async'), carrier = require('carrier');async.parallel({ input: fs.openFile.bind(null, './input.txt', 'r'), output: fs.openFile.bind(null, './output.txt', 'a')}, function (err, result) { if (err) { console.log("An error occured: " + err); return; } carrier.carry(result.input) .on('line', result.output.write) .on('end', function () { result.output.end(); console.log("Done"); });});
