我所需要做的就是在当前函数执行结束时执行一个回调函数。
function LoadData()
{
alert('The data has been loaded');
//Call my callback with parameters. For example,
//callback(loadedData , currentObject);
}
这个函数的消费者应该是这样的:
object.LoadData(success);
function success(loadedData , currentObject)
{
//Todo: some action here
}
我怎么实现这个呢?
当前回答
function loadData(callback) {
//execute other requirement
if(callback && typeof callback == "function"){
callback();
}
}
loadData(function(){
//execute callback
});
其他回答
实际上，你的代码会像现在一样工作，只是把你的回调声明为一个参数，你可以直接使用参数名调用它。
最基本的
function doSomething(callback) {
// ...
// Call the callback
callback('stuff', 'goes', 'here');
}
function foo(a, b, c) {
// I'm the callback
alert(a + " " + b + " " + c);
}
doSomething(foo);
它会调用doSomething，它会调用foo，它会提醒"东西在这里"
注意，传递函数引用(foo)非常重要，而不是调用函数并传递其结果(foo())。在你的问题中，你做得很好，但值得指出的是，这是一个常见的错误。
更高级的东西
有时候你想调用回调让它看到这个的特定值。你可以用JavaScript调用函数轻松地做到这一点:
function Thing(name) {
this.name = name;
}
Thing.prototype.doSomething = function(callback) {
// Call our callback, but using our own instance as the context
callback.call(this);
}
function foo() {
alert(this.name);
}
var t = new Thing('Joe');
t.doSomething(foo); // Alerts "Joe" via `foo`
你也可以传递参数:
function Thing(name) {
this.name = name;
}
Thing.prototype.doSomething = function(callback, salutation) {
// Call our callback, but using our own instance as the context
callback.call(this, salutation);
}
function foo(salutation) {
alert(salutation + " " + this.name);
}
var t = new Thing('Joe');
t.doSomething(foo, 'Hi'); // Alerts "Hi Joe" via `foo`
有时，将想要给回调函数的参数作为数组传递，而不是单独传递，是很有用的。你可以使用apply来做到这一点:
function Thing(name) {
this.name = name;
}
Thing.prototype.doSomething = function(callback) {
// Call our callback, but using our own instance as the context
callback.apply(this, ['Hi', 3, 2, 1]);
}
function foo(salutation, three, two, one) {
alert(salutation + " " + this.name + " - " + three + " " + two + " " + one);
}
var t = new Thing('Joe');
t.doSomething(foo); // Alerts "Hi Joe - 3 2 1" via `foo`
在尝试执行回调函数之前，最好确保它是一个实际的函数:
if (callback && typeof(callback) === "function") {
callback();
}
function loadData(callback) {
//execute other requirement
if(callback && typeof callback == "function"){
callback();
}
}
loadData(function(){
//execute callback
});
如果你想在某件事完成时执行一个函数。一个很好的解决方案是监听事件。 例如，我将实现一个Dispatcher，一个DispatcherEvent类与ES6，然后:
let Notification = new Dispatcher()
Notification.on('Load data success', loadSuccessCallback)
const loadSuccessCallback = (data) =>{
...
}
//trigger a event whenever you got data by
Notification.dispatch('Load data success')
调度员:
class Dispatcher{
constructor(){
this.events = {}
}
dispatch(eventName, data){
const event = this.events[eventName]
if(event){
event.fire(data)
}
}
//start listen event
on(eventName, callback){
let event = this.events[eventName]
if(!event){
event = new DispatcherEvent(eventName)
this.events[eventName] = event
}
event.registerCallback(callback)
}
//stop listen event
off(eventName, callback){
const event = this.events[eventName]
if(event){
delete this.events[eventName]
}
}
}
DispatcherEvent:
class DispatcherEvent{
constructor(eventName){
this.eventName = eventName
this.callbacks = []
}
registerCallback(callback){
this.callbacks.push(callback)
}
fire(data){
this.callbacks.forEach((callback=>{
callback(data)
}))
}
}
编码快乐!
p/s:我的代码缺少处理一些错误异常
我的2美分，相同但不同…
<script>
dosomething("blaha", function(){
alert("Yay just like jQuery callbacks!");
});
function dosomething(damsg, callback){
alert(damsg);
if(typeof callback == "function")
callback();
}
</script>
