function LoadData(callback) 
{
    alert('the data have been loaded');
    callback(loadedData, currentObject);
}

当调用回调函数时，我们可以像下面这样使用它:

consumingFunction (callbackFunctionName)

例子:

// Callback function only know the action,
// but don't know what's the data.
function callbackFunction(unknown) {
  console.log(unknown);
}

// This is a consuming function.
function getInfo(thenCallback) {
  // When we define the function we only know the data but not
  // the action. The action will be deferred until excecuting.
  var info = 'I know now';
  if (typeof thenCallback === 'function') {
    thenCallback(info);    
  }
}

// Start.
getInfo(callbackFunction); // I know now

这是Codepend的完整示例。

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 login(email, password, callback) {
         //verify the user
         const users = [
          { email: "abc@gmail.com", password: "123" },
          { email: "xyz@gmail.com", password: "xyz" }
         ];

         const user = users.find(
           (user) => user.email === email && user.password === password
         );
         callback(user);
       `enter code here`}

    function redirect(user) {
       if (user) {
          //user is successfully logged in
          console.log("user is successfully logged in ");
       } else {
         console.log("Incorrect credentials ");
       } 
    }

    
    login("abc@gmail.com", "123", redirect);

我希望这个例子能帮助所有想了解JS中回调的人

Try:

function LoadData (callback)
{
    // ... Process whatever data
    callback (loadedData, currentObject);
}

函数是JavaScript中的第一类;你可以四处传阅。

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