问题
I want to do:
$(\"img\").bind(\'load\', function() {
// do stuff
});
But the load event doesn\'t fire when the image is loaded from cache. The jQuery docs suggest a plugin to fix this, but it doesn\'t work
回答1:
If the src is already set, then the event is firing in the cached case, before you even get the event handler bound. To fix this, you can loop through checking and triggering the event based off .complete, like this:
$("img").one("load", function() {
// do stuff
}).each(function() {
if(this.complete) {
$(this).load(); // For jQuery < 3.0
// $(this).trigger('load'); // For jQuery >= 3.0
}
});
Note the change from .bind() to .one() so the event handler doesn't run twice.
回答2:
Can I suggest that you reload it into a non-DOM image object? If it's cached, this will take no time at all, and the onload will still fire. If it isn't cached, it will fire the onload when the image is loaded, which should be the same time as the DOM version of the image finishes loading.
Javascript:
$(document).ready(function() {
var tmpImg = new Image() ;
tmpImg.src = $('#img').attr('src') ;
tmpImg.onload = function() {
// Run onload code.
} ;
}) ;
Updated (to handle multiple images and with correctly ordered onload attachment):
$(document).ready(function() {
var imageLoaded = function() {
// Run onload code.
}
$('#img').each(function() {
var tmpImg = new Image() ;
tmpImg.onload = imageLoaded ;
tmpImg.src = $(this).attr('src') ;
}) ;
}) ;
回答3:
My simple solution, it doesn't need any external plugin and for common cases should be enough:
/**
* Trigger a callback when the selected images are loaded:
* @param {String} selector
* @param {Function} callback
*/
var onImgLoad = function(selector, callback){
$(selector).each(function(){
if (this.complete || /*for IE 10-*/ $(this).height() > 0) {
callback.apply(this);
}
else {
$(this).on('load', function(){
callback.apply(this);
});
}
});
};
use it like this:
onImgLoad('img', function(){
// do stuff
});
for example, to fade in your images on load you can do:
$('img').hide();
onImgLoad('img', function(){
$(this).fadeIn(700);
});
Or as alternative, if you prefer a jquery plugin-like approach:
/**
* Trigger a callback when 'this' image is loaded:
* @param {Function} callback
*/
(function($){
$.fn.imgLoad = function(callback) {
return this.each(function() {
if (callback) {
if (this.complete || /*for IE 10-*/ $(this).height() > 0) {
callback.apply(this);
}
else {
$(this).on('load', function(){
callback.apply(this);
});
}
}
});
};
})(jQuery);
and use it in this way:
$('img').imgLoad(function(){
// do stuff
});
for example:
$('img').hide().imgLoad(function(){
$(this).fadeIn(700);
});
回答4:
Do you really have to do it with jQuery? You can attach the onload event directly to your image as well;
<img src="/path/to/image.jpg" onload="doStuff(this);" />
It will fire every time the image has loaded, from cache or not.
回答5:
You can also use this code with support for loading error:
$("img").on('load', function() {
// do stuff on success
})
.on('error', function() {
// do stuff on smth wrong (error 404, etc.)
})
.each(function() {
if(this.complete) {
$(this).load();
} else if(this.error) {
$(this).error();
}
});
回答6:
I just had this problem myself, searched everywhere for a solution that didn't involve killing my cache or downloading a plugin.
I didn't see this thread immediately so I found something else instead which is an interesting fix and (I think) worthy of posting here:
$('.image').load(function(){
// stuff
}).attr('src', 'new_src');
I actually got this idea from the comments here: http://www.witheringtree.com/2009/05/image-load-event-binding-with-ie-using-jquery/
I have no idea why it works but I have tested this on IE7 and where it broke before it now works.
Hope it helps,
Edit
The accepted answer actually explains why:
If the src is already set then the event is firing in the cache cased before you get the event handler bound.
回答7:
A solution I found https://bugs.chromium.org/p/chromium/issues/detail?id=7731#c12 (This code taken directly from the comment)
var photo = document.getElementById('image_id');
var img = new Image();
img.addEventListener('load', myFunction, false);
img.src = 'http://newimgsource.jpg';
photo.src = img.src;
回答8:
A modification to GUS's example:
$(document).ready(function() {
var tmpImg = new Image() ;
tmpImg.onload = function() {
// Run onload code.
} ;
tmpImg.src = $('#img').attr('src');
})
Set the source before and after the onload.
回答9:
By using jQuery to generate a new image with the image's src, and assigning the load method directly to that, the load method is successfully called when jQuery finishes generating the new image. This is working for me in IE 8, 9 and 10
$('<img />', {
"src": $("#img").attr("src")
}).load(function(){
// Do something
});
回答10:
Just re-add the src argument on a separate line after the img oject is defined. This will trick IE into triggering the lad-event. It is ugly, but it is the simplest workaround I've found so far.
jQuery('<img/>', {
src: url,
id: 'whatever'
})
.load(function() {
})
.appendTo('#someelement');
$('#whatever').attr('src', url); // trigger .load on IE
回答11:
I can give you a little tip if you want do like this:
<div style="position:relative;width:100px;height:100px">
<img src="loading.jpg" style='position:absolute;width:100px;height:100px;z-index:0'/>
<img onLoad="$(this).fadeIn('normal').siblings('img').fadeOut('normal')" src="picture.jpg" style="display:none;position:absolute;width:100px;height:100px;z-index:1"/>
</div>
If you do that when the browser caches pictures, it's no problem always img shown but loading img under real picture.
回答12:
I had this problem with IE where the e.target.width would be undefined. The load event would fire but I couldn't get the dimensions of the image in IE (chrome + FF worked).
Turns out you need to look for e.currentTarget.naturalWidth & e.currentTarget.naturalHeight.
Once again, IE does things it's own (more complicated) way.
回答13:
You can solve your problem using JAIL plugin that also allows you to lazy load images (improving the page performance) and passing the callback as parameter
$('img').asynchImageLoader({callback : function(){...}});
The HTML should look like
<img name="/global/images/sample1.jpg" src="/global/images/blank.gif" width="width" height="height" />
回答14:
If you want a pure CSS solution, this trick works very well - use the transform object. This also works with images when they're cached or not:
CSS:
.main_container{
position: relative;
width: 500px;
height: 300px;
background-color: #cccccc;
}
.center_horizontally{
position: absolute;
width: 100px;
height: 100px;
background-color: green;
left: 50%;
top: 0;
transform: translate(-50%,0);
}
.center_vertically{
position: absolute;
top: 50%;
left: 0;
width: 100px;
height: 100px;
background-color: blue;
transform: translate(0,-50%);
}
.center{
position: absolute;
top: 50%;
left: 50%;
width: 100px;
height: 100px;
background-color: red;
transform: translate(-50%,-50%);
}
HTML:
<div class="main_container">
<div class="center_horizontally"></div>
<div class="center_vertically"></div>
<div class="center"></div>
</div>
</div
Codepen example
Codepen LESS example
来源：https://stackoverflow.com/questions/3877027/jquery-callback-on-image-load-even-when-the-image-is-cached