试试这个方法。在Java脚本函数中进行循环以等待ajax调用完成。

function getLabelById(id)
{
    var label = '';
    var done = false;
    $.ajax({
       cache: false,
       url: "YourMvcActionUrl",
       type: "GET",
       dataType: "json",
       async: false,
       error: function (result) {
         label='undefined';
         done = true;
        },
       success: function (result) {
            label = result.Message;
            done = true;
        }
     });

   //A loop to check done if ajax call is done.
   while (!done)
   {
      setTimeout(function(){ },500); // take a sleep.
   }

    return label;
}

为了扩展Alex的回答，我举了一个带有可变论点和承诺的例子。我想通过ajax加载图像，并在它们全部加载后显示在页面上。

为了做到这一点，我使用了以下方法:

let urlCreator = window.URL || window.webkitURL;

// Helper function for making ajax requests
let fetch = function(url) {
    return $.ajax({
        type: "get",
        xhrFields: {
            responseType: "blob"
        },
        url: url,
    });
};

// Map the array of urls to an array of ajax requests
let urls = ["https://placekitten.com/200/250", "https://placekitten.com/300/250"];
let files = urls.map(url => fetch(url));

// Use the spread operator to wait for all requests
$.when(...files).then(function() {
    // If we have multiple urls, then loop through
    if(urls.length > 1) {
        // Create image urls and tags for each result
        Array.from(arguments).forEach(data => {
            let imageUrl = urlCreator.createObjectURL(data[0]);
            let img = `<img src=${imageUrl}>`;
            $("#image_container").append(img);
        });
    }
    else {
        // Create image source and tag for result
        let imageUrl = urlCreator.createObjectURL(arguments[0]);
        let img = `<img src=${imageUrl}>`;
        $("#image_container").append(img);
    }
});

更新工作的单个或多个url: https://jsfiddle.net/euypj5w9/

在@BBonifield回答的基础上，我写了一个实用函数，这样信号量逻辑就不会分布在所有ajax调用中。

untilAjax是一个实用函数，它在所有ajaxCalls完成后调用回调函数。

ajaxObjs是一个ajax设置对象的数组[http://api.jquery.com/jQuery.ajax/]。

Fn是回调函数

function untilAjax(ajaxObjs, fn) {
  if (!ajaxObjs || !fn) {
    return;
  }
  var ajaxCount = ajaxObjs.length,
    succ = null;

  for (var i = 0; i < ajaxObjs.length; i++) { //append logic to invoke callback function once all the ajax calls are completed, in success handler.
    succ = ajaxObjs[i]['success'];
    ajaxObjs[i]['success'] = function(data) { //modified success handler
      if (succ) {
        succ(data);
      }
      ajaxCount--;
      if (ajaxCount == 0) {
        fn(); //modify statement suitably if you want 'this' keyword to refer to another object
      }
    };
    $.ajax(ajaxObjs[i]); //make ajax call
    succ = null;
  };

示例:doSomething函数使用untilAjax。

function doSomething() {
  // variable declarations
  untilAjax([{
    url: 'url2',
    dataType: 'json',
    success: function(data) {
      //do something with success data
    }
  }, {
    url: 'url1',
    dataType: 'json',
    success: function(data) {
      //do something with success data
    }
  }, {
    url: 'url2',
    dataType: 'json',
    success: function(response) {
      //do something with success data
    }
  }], function() {
    // logic after all the calls are completed.
  });
}

试试这个方法。在Java脚本函数中进行循环以等待ajax调用完成。

function getLabelById(id)
{
    var label = '';
    var done = false;
    $.ajax({
       cache: false,
       url: "YourMvcActionUrl",
       type: "GET",
       dataType: "json",
       async: false,
       error: function (result) {
         label='undefined';
         done = true;
        },
       success: function (result) {
            label = result.Message;
            done = true;
        }
     });

   //A loop to check done if ajax call is done.
   while (!done)
   {
      setTimeout(function(){ },500); // take a sleep.
   }

    return label;
}

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>

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