mobile safari - reliable callback for when Image loads?

问题

I try to load an image as such:

var img = new Image();
img.src = 'mars.png';
img.onLoad = callback;


function callback(){
    // doesnt fire
       alert("loaded");
}

the callback never fires, whats the workaround?

回答1:

You MUST define the onload BEFORE you change the src and event handlers are lowercase so it is spelled onload

var img = new Image();
img.onload = callback;
img.src = 'mars.png';

function callback(){
  alert("loaded");
}

or as I prefer it

var img = new Image();
img.onload = function(){
  alert("loaded");
}
img.src = 'mars.png';

回答2:

Have you tried these?

var img = new Image();
img.src = 'mars.png';
img.onLoad = function(){
    // doesnt fire
       alert("loaded");
};

回答3:

mplungjan is right you can use these instead:

img.onload = function(){
    // doesnt fire
       alert("loaded");
};

with lower l in onLoad

来源：https://stackoverflow.com/questions/11805945/mobile-safari-reliable-callback-for-when-image-loads