Question

我想在$.when()函数中（在发出请求之前）对每个延迟请求应用一个条件。但是，在if中放置$.when条件会返回错误。

做什么是我实质上描述的正确方法？

$.when(
  if(var1) {
    $.getJSON(url1, function(data) {...}),
  },
  if(var2) {
    $.getJSON(url2, function(data) {...}),
  },
  if(varN) {
    $.getJSON(urlN, function(data) {...}),
  },
).then(function() {
  ...
});

Answer 1

您可以简单地构造一个AJAX承诺数组。之后，使用$.when.apply($, <yourArray>)。为了说明解决方案，这里有一个基于您提供的代码的示例：

// Construct array to store requests
var requests = [];

// Conditionally push your deferred objets into the array
if(var1) requests.push($.getJSON(url1, function(data) {...}));
if(var2) requests.push($.getJSON(url2, function(data) {...}));
if(var3) requests.push($.getJSON(url3, function(data) {...}));

// Apply array to $.when()
$.when.apply($, requests).then(function() {
  // Things to do when all is done
});

请注意，这是一个显示概念验证示例的代码段：我使用JSONPlaceholder返回的虚拟JSON：

＆＃13;

$(function() {
  // Construct array to store requests
  var requests = [];
  
  // Conditional vars
  var var1 = true,
      var2 = false,
      var3 = true;

  // Conditionally push your deferred objets into the array
  if (var1) requests.push($.get('https://jsonplaceholder.typicode.com/posts/1', function(data) {  return data;
  }));
  if (var2) requests.push($.get('https://jsonplaceholder.typicode.com/posts/2', function(data) {  return data;
  }));
  if (var3) requests.push($.get('https://jsonplaceholder.typicode.com/posts/3', function(data) {  return data;
  }));

  // Apply array to $.when()
  $.when.apply($, requests).then(function(d) {
  
    // Log returned data
    var objects = arguments;
    console.log(objects);
  });
});

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

＆＃13;

Answer 2

您可以在$ when（）中使用三元运算符。以下代码对我有用：

var includeX = true, includeY = false;
var x = $.get('check.html');
var y = $('div').animate({height: '200px'}, 3000).promise(); // you may use an ajax request also here
$.when(includeX ? x : '',  includeY ? y: '').done(function(){
    console.log(x);
    console.log(y);
    console.log('done');
})

将条件应用于jQuery.when（）延迟函数

2 个答案: