本文實例講述了node.js實現回調的方法。分享給大家供大家參考，具體如下：

向回調函數傳遞額外的參數

在調用函數中，使用匿名函數中實現需傳遞的參數，再次匿名函數內調用回調函數。

var events = require("events");function CarShow() {  events.EventEmitter.call(this);  this.seeCar = function (make) {    this.emit('sawCar', make);  }}CarShow.prototype.__proto__ = events.EventEmitter.prototype;var show = new CarShow();function logCar(make) {  console.log("Saw a "+make);}function logColorCar(make, color) {  console.log("Saw a %s %s ", color, make);}show.on("sawCar", logCar);show.on("sawCar", function (make) {  var colors = ["red", "blue", "black", "pink", "green"];  var color = colors[Math.floor(Math.random()*3)];  logColorCar(make, color);});show.seeCar("Ferrari");show.seeCar("Porsche");show.seeCar("Bugatti");

在回調中實現閉包

如果某個回調函數需要訪問父函數的作用域的變量，就需要使用閉包，在函數塊內部封裝一個異步調用，并傳入所需要的變量。

function logCar(logMsg, callback) {  process.nextTick(function () {    callback(logMsg);  });}var cars = ["獵豹", "捷達", "朗逸"];for(var idx in cars){  var msg = "Saw a "+cars[idx];  logCar(msg, function () {    console.log("Normal Callback "+ msg);  });}for(var idx in cars){  var msg = "Saw a "+cars[idx];  (function (msg) {    logCar(msg, function () {      console.log("Closure Callback "+ msg);    })  })(msg);}//Normal Callback Saw a 朗逸//Normal Callback Saw a 朗逸//Normal Callback Saw a 朗逸//Closure Callback Saw a 獵豹//Closure Callback Saw a 捷達//Closure Callback Saw a 朗逸

鏈式回調

使用異步函數時，如果兩個函數都在事件隊列上，則無法保證它們的運行順序。解決方法是讓來自異步函數的回調再次調用該函數，直到沒有更多的工作要做，以執行鏈式回調。

function logCar(car, callback) {  console.log("Saw a %$", car);  if(cars.length){    process.nextTick(function () {      callback();    });  }}function logCars(cars) {  var car = cars.pop();  logCar(car, function () {    logCars(cars);  });}var cars = ["獵豹", "捷達", "朗逸"];logCars(cars);

希望本文所述對大家nodejs程序設計有所幫助。