Javascript : passing a function as an argument

问题

I want to load a default image if an image fails to load. I also want to call getLoadComplete() once the image has loaded. How do I pass the this.getLoadComplete() function into the function called on img.onerror?

Here is the code I've got:

    img.onload = this.getLoadComplete();

    img.onerror = function(){
        img.src = "http://xxxx.com/image.gif";
     }

     img.src = request.url;

回答1:

img.onload = this.getLoadComplete();

You're invoking getLoadComplete() immediately, and assigning its return value to img.onload. You probably want this:

img.onload = this.getLoadComplete;

That is, set img.onload to the function itself, not its return value.

You don't need to do anything special in onerror; the onload handler will still be set to getLoadComplete, and when you modify the src in your onerror handler, it will invoke onload after the fallback image is loaded.

回答2:

you just need to call the function.

img.onload = this.getLoadComplete();

img.onerror = function(){
    img.src = "http://www.3d-maps-minus-3d.com/img/unavailable.gif";
this.getLoadComplete();
 }

来源：https://stackoverflow.com/questions/19643528/javascript-passing-a-function-as-an-argument