圖片預加載回調射擊所有圖像都加載之前

Question

問題：

我試圖做的圖像預加載，發現this awesome solution我試圖adapt.I了代碼，幷包裹在一個函數返回一個承諾，但我注意到done()處理程序被稱爲之前所有的圖像被加載，我做錯了什麼？

代碼：

function preload(args) { 

    var $defer = $.Deferred(); 
    var preload = args; 
    var promises = []; 
    for (var i = 0; i < preload.length; i++) { 
    (function(url, promise) { 
     var img = new Image(); 
     img.onload = function() { 
     promise.resolve(); 
     console.log("loaded:" + url); 
     }; 
     console.log("loading:" + url); 
     img.src = url; 
    })(preload[i], promises[i] = $.Deferred()); 
    } 
    $.when.apply($, promises).done(function() { 
    console.log("All images ready sir!"); 
    $defer.resolve(); 
    }); 

    return $defer; 
} 

var images = ['https://pbs.twimg.com/media/CbM1w65UcAAKfSJ.jpg', 'https://www.kenrockwell.com/nikon/d600/sample-images/600_0985.JPG', 'https://developer.nvidia.com/sites/default/files/akamai/gameworks/blog/GameWorks_Vulkan_and_OpenGL_Samples/vulkan2.png', 'https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcSKJ1fJHxLQ6unFkHZnHJoT-RfqrBvWMrzhmRFAPUt0VvdvZSDd', 'https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcTyvamruO8NCTeQJXtQaXM8xEQS5P9ANh_npfgZpv-7x8ISvzX5zg']; 

preload(images).done(function() { 
    console.log("OK, begin business process.."); 

}); 

控制檯輸出：

的jsfiddle：

https://jsfiddle.net/sajjansarkar/f5k94n2r/

Answer 1

交換這兩行

promise.resolve(); 
    console.log("loaded:" + url); 

許是解決觸發決心鏈的其餘部分。然後添加日誌消息。