如果你需要简单的东西;Once and done回调

        //multiple ajax calls above
        var callback = function () {
            if ($.active !== 0) {
                setTimeout(callback, '500');
                return;
            }
            //whatever you need to do here
            //...
        };
        callback();

正如其他答案所提到的，你可以使用ajaxStop()等待直到所有ajax请求完成。

$(document).ajaxStop(function() {
     // This function will be triggered every time any ajax request is requested and completed
});

如果你想为特定的ajax()请求做这件事，你能做的最好的是在特定的ajax请求中使用complete()方法:

$.ajax({
    type: "POST",
    url: "someUrl",
    success: function(data) {
        // This function will be triggered when ajax returns a 200 status code (success)
    },
    complete: function() {
        // This function will be triggered always, when ajax request is completed, even it fails/returns other status code
    },
    error: function() {
        // This will be triggered when ajax request fail.
    }
});

但是，如果你只需要等待几个和特定的ajax请求被完成?使用美妙的javascript承诺等待，直到这些ajax你想等待完成。我做了一个简单易读的示例，向您展示promises如何与ajax一起工作。请看下一个例子。我使用setTimeout来阐明这个示例。

// Note: // resolve() is used to mark the promise as resolved // reject() is used to mark the promise as rejected $(document).ready(function() { $("button").on("click", function() { var ajax1 = new Promise((resolve, reject) => { $.ajax({ type: "GET", url: "https://miro.medium.com/max/1200/0*UEtwA2ask7vQYW06.png", xhrFields: { responseType: 'blob'}, success: function(data) { setTimeout(function() { $('#image1').attr("src", window.URL.createObjectURL(data)); resolve(" Promise ajax1 resolved"); }, 1000); }, error: function() { reject(" Promise ajax1 rejected"); }, }); }); var ajax2 = new Promise((resolve, reject) => { $.ajax({ type: "GET", url: "https://cdn1.iconfinder.com/data/icons/social-media-vol-1-1/24/_github-512.png", xhrFields: { responseType: 'blob' }, success: function(data) { setTimeout(function() { $('#image2').attr("src", window.URL.createObjectURL(data)); resolve(" Promise ajax2 resolved"); }, 1500); }, error: function() { reject(" Promise ajax2 rejected"); }, }); }); var ajax3 = new Promise((resolve, reject) => { $.ajax({ type: "GET", url: "https://miro.medium.com/max/632/1*LUfpOf7teWvPdIPTBmYciA.png", xhrFields: { responseType: 'blob' }, success: function(data) { setTimeout(function() { $('#image3').attr("src", window.URL.createObjectURL(data)); resolve(" Promise ajax3 resolved"); }, 2000); }, error: function() { reject(" Promise ajax3 rejected"); }, }); }); Promise.all([ajax1, ajax2, ajax3]).then(values => { console.log("We waited until ajax ended: " + values); console.log("My few ajax ended, lets do some things!!") }, reason => { console.log("Promises failed: " + reason); }); // Or if you want wait for them individually do it like this // ajax1.then(values => { // console.log("Promise 1 resolved: " + values) // }, reason => { // console.log("Promise 1 failed: " + reason) // }); }); }); img { max-width: 200px; max-height: 100px; } <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <button>Make AJAX request</button> <div id="newContent"> <img id="image1" src=""> <img id="image2" src=""> <img id="image3" src=""> </div>

使用ajaxStop事件。

例如，假设你有一个载入…消息，同时获取100个ajax请求，你想隐藏该消息一旦加载。

jQuery文档:

$("#loading").ajaxStop(function() {
  $(this).hide();
});

请注意，它将等待所有ajax请求在该页面上完成。

我找到了一个很好的答案，这正是我在寻找的:)

jQuery ajaxQueue

//This handles the queues    
(function($) {

  var ajaxQueue = $({});

  $.ajaxQueue = function(ajaxOpts) {

    var oldComplete = ajaxOpts.complete;

    ajaxQueue.queue(function(next) {

      ajaxOpts.complete = function() {
        if (oldComplete) oldComplete.apply(this, arguments);

        next();
      };

      $.ajax(ajaxOpts);
    });
  };

})(jQuery);

然后你可以像这样向队列添加一个ajax请求:

$.ajaxQueue({
        url: 'page.php',
        data: {id: 1},
        type: 'POST',
        success: function(data) {
            $('#status').html(data);
        }
    });

我的解决方案如下

var request;
...
'services': {
  'GetAddressBookData': function() {
    //This is the primary service that loads all addressbook records 
    request = $.ajax({
      type: "POST",
      url: "Default.aspx/GetAddressBook",
      contentType: "application/json;",
      dataType: "json"
    });
  },

  ...

  'apps': {
    'AddressBook': {
      'data': "",
      'Start': function() {
          ...services.GetAddressBookData();
          request.done(function(response) {
            trace("ajax successful");
            ..apps.AddressBook.data = response['d'];
            ...apps.AddressBook.Filter();
          });
          request.fail(function(xhr, textStatus, errorThrown) {
            trace("ajax failed - " + errorThrown);
          });

工作得很顺利。我已经尝试了许多不同的方法，但我发现这是最简单和最可重用的方法。希望能有所帮助

如果从头开始，我强烈建议使用$.when()。

尽管这个问题有超过一百万个答案，但我仍然没有找到任何对我的情况有用的答案。假设您必须处理现有的代码库，已经进行了一些ajax调用，并且不想引入承诺的复杂性和/或重做整个事情。

我们可以很容易地利用jQuery的.data， .on和.trigger函数，这些函数一直是jQuery的一部分。

Codepen

我的解决方案的优点是:

显然回调依赖于什么 函数triggerNowOrOnLoaded并不关心数据是否已经加载或我们仍在等待它 将其插入现有代码非常容易

$(function() { // wait for posts to be loaded triggerNowOrOnLoaded("posts", function() { var $body = $("body"); var posts = $body.data("posts"); $body.append("<div>Posts: " + posts.length + "</div>"); }); // some ajax requests $.getJSON("https://jsonplaceholder.typicode.com/posts", function(data) { $("body").data("posts", data).trigger("posts"); }); // doesn't matter if the `triggerNowOrOnLoaded` is called after or before the actual requests $.getJSON("https://jsonplaceholder.typicode.com/users", function(data) { $("body").data("users", data).trigger("users"); }); // wait for both types triggerNowOrOnLoaded(["posts", "users"], function() { var $body = $("body"); var posts = $body.data("posts"); var users = $body.data("users"); $body.append("<div>Posts: " + posts.length + " and Users: " + users.length + "</div>"); }); // works even if everything has already loaded! setTimeout(function() { // triggers immediately since users have been already loaded triggerNowOrOnLoaded("users", function() { var $body = $("body"); var users = $body.data("users"); $body.append("<div>Delayed Users: " + users.length + "</div>"); }); }, 2000); // 2 seconds }); // helper function function triggerNowOrOnLoaded(types, callback) { types = $.isArray(types) ? types : [types]; var $body = $("body"); var waitForTypes = []; $.each(types, function(i, type) { if (typeof $body.data(type) === 'undefined') { waitForTypes.push(type); } }); var isDataReady = waitForTypes.length === 0; if (isDataReady) { callback(); return; } // wait for the last type and run this function again for the rest of the types var waitFor = waitForTypes.pop(); $body.on(waitFor, function() { // remove event handler - we only want the stuff triggered once $body.off(waitFor); triggerNowOrOnLoaded(waitForTypes, callback); }); } <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <body>Hi!</body>