javascript - How do I make an image load synchronously?

Question

I want to create an object that has an image property, but I want the contstructor to finish running only once the image is loaded. Or to describe this with code:

GraphicObject = Class.extend({

    //This is the constructor
    init: function(){
          this.graphic = new Image();
          this.graphic.src = 'path/to/file.png';

          while(true)
          {
              this.graphic.onload = function(){break;};
              //I know this won't work since the 'break' is on a different context
              //but you got what I try to do.
          }
     }


})

For those who are unfamiliar with the Class notation I'm using in my script, it's based on this

Any ideas?

Answer 1

It is possible, but only with the ancient art of Base64 and Data-URL.

GIF image converted to Base64.

rune.b64

R0lGODlhIwAjAIAAAP///wAAACwAAAAAIwAjAAACf4SPqcsb3R40ocpJK7YaA35FnPdZGxg647kyqId2SQzHqdlCdgdmqcvbHXKi4AthYiGPvp9KVuoNocWLMOpUtHaS5CS54mZntiWNRWymn14tU7c2t6ukOJlKR5OiNTzQ7wb41LdnJ1coeNg3pojGqFZniPU4lTi0d4mpucmpUAAAOw==

JavaScript which loads the converted image form the same server via blocking AJAX.

loader.js

var request = new XMLHttpRequest();
var image = document.createElement('img');

request.open('GET', 'rune.b64', false);
request.send(null);

if (request.status === 200) {
  image.src= 'data:image/gif;base64,' + request.responseText.trim();

  document.getElementsByTagName("body")[0].appendChild(image); 
}

Problems

• Some older browsers don't like (big) Data-URLs
• Base64 encoding makes images about 37% bigger
• The whole UI is blocked till the image is loaded

This is a very-evil way