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 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

其他回答

   function callback(e){
      return e;
   }
    var MyClass = {
       method: function(args, callback){
          console.log(args);
          if(typeof callback == "function")
          callback();
       }    
    }

==============================================

MyClass.method("hello",function(){
    console.log("world !");
});

==============================================

结果是:

hello world !

有些答案虽然正确,但理解起来可能有点棘手。下面是一个外行术语的例子:

var users = ["Sam", "Ellie", "Bernie"];

function addUser(username, callback)
{
    setTimeout(function()
    {
        users.push(username);
        callback();
    }, 200);
}

function getUsers()
{
    setTimeout(function()
    {
        console.log(users);
    }, 100);
}

addUser("Jake", getUsers);

回调意味着,在使用console.log显示用户列表之前,总是将“Jake”添加到用户中。

源(YouTube)

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。

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

    //execute other requirement

    if(callback && typeof callback == "function"){
        callback();
   }
}

loadData(function(){

   //execute callback

});