Best way to retrieve image from server using ajax [duplicate] - asp.net

Question

Is it possible to reload an image with an identical file name from a server using jQuery?
For example, I have an image on a page, however, the physical image can change based on user actions. Note, this does not mean the file name changes, but the actual file itself.
ie:
User views image on default page
User uploads new image
Default image on page does not change(I assume this is due to the file name being identical, the browser uses the cached version)
Regardless of how often the code below is called, the same issue persists.
$("#myimg").attr("src", "/myimg.jpg");
In the jQuery documentation, the "load" function would be perfect if it had a default method of firing the event as opposed to binding a callback function to a successful/complete load of an element.
Any assistance is greatly appreciated.

Answer 1

It sounds like it's your browser caching the image (which I now notice you wrote in your question). You can force the browser to reload the image by passing an extra variable like so:
d = new Date();
$("#myimg").attr("src", "/myimg.jpg?"+d.getTime());

Answer 2

It's probably not the best way, but I've solved this problem in the past by simply appending a timestamp to the image URL using JavaScript:
$("#myimg").attr("src", "/myimg.jpg?timestamp=" + new Date().getTime());
Next time it loads, the timestamp is set to the current time and the URL is different, so the browser does a GET for the image instead of using the cached version.

Answer 3

This could be one of the two problems you mention yourself.
The server is caching the image
The jQuery does not fire or at least doesn't update the attribute
To be honest, I think it's number two. Would be a lot easier if we could see some more jQuery. But for a start, try remove the attribute first, and then set it again. Just to see if that helps:
$("#myimg").removeAttr("src").attr("src", "/myimg.jpg");
Even if this works, post some code since this is not optimal, imo :-)

Answer 4

with one line with no worries about hardcoding the image src into the javascript (thanks to jeerose for the ideas:
$("#myimg").attr("src", $("#myimg").attr("src")+"?timestamp=" + new Date().getTime());

Answer 5

To bypass caching and avoid adding infinite timestamps to the image url, strip the previous timestamp before adding a new one, this is how I've done it.
//refresh the image every 60seconds
var xyro_refresh_timer = setInterval(xyro_refresh_function, 60000);
function xyro_refresh_function(){
//refreshes an image with a .xyro_refresh class regardless of caching
//get the src attribute
source = jQuery(".xyro_refresh").attr("src");
//remove previously added timestamps
source = source.split("?", 1);//turns "image.jpg?timestamp=1234" into "image.jpg" avoiding infinitely adding new timestamps
//prep new src attribute by adding a timestamp
new_source = source + "?timestamp=" + new Date().getTime();
//alert(new_source); //you may want to alert that during developement to see if you're getting what you wanted
//set the new src attribute
jQuery(".xyro_refresh").attr("src", new_source);
}

Answer 6

This works great! however if you reload the src multiple times, the timestamp gets concatenated to the url too. I've modified the accepted answer to deal with that.
$('#image_reload_button').on('click', function () {
var img = $('#your_image_selector');
var src = img.attr('src');
var i = src.indexOf('?dummy=');
src = i != -1 ? src.substring(0, i) : src;
var d = new Date();
img.attr('src', src + '?dummy=' + d.getTime());
});

Answer 7

Have you tried resetting the image containers html. Of course if it's the browser that is caching then this wouldn't help.
function imageUploadComplete () {
$("#image_container").html("<img src='" + newImageUrl + "'>");
}

Answer 8

Some times actually solution like -
$("#Image").attr("src", $('#srcVal').val()+"&"+Math.floor(Math.random()*1000));
also not refresh src properly, try out this, it worked for me ->
$("#Image").attr("src", "dummy.jpg");
$("#Image").attr("src", $('#srcVal').val()+"&"+Math.floor(Math.random()*1000));

Answer 9

Using "#" as a delimiter might be useful
My images are kept in a "hidden" folder above "www" so that only logged users are allowed access to them. For this reason I cannot use the ordinary <img src=/somefolder/1023.jpg> but I send requests to the server like <img src=?1023> and it responds by sending back the image kept under name '1023'.
The application is used for image cropping, so after an ajax request to crop the image, it is changed as content on the server but keeps its original name. In order to see the result of the cropping, after the ajax request has been completed, the first image is removed from the DOM and a new image is inserted with the same name <img src=?1023>.
To avoid cashing I add to the request the "time" tag prepended with "#" so it becomes like <img src=?1023#1467294764124>. The server automatically filters out the hash part of the request and responds correctly by sending back my image kept as '1023'. Thus I always get the last version of the image without much server-side decoding.

Answer 10

Based on #kasper Taeymans' answer.
If u simply need reload image (not replace it's src with smth new), try:
$(function() {
var img = $('#img');
var refreshImg = function(img) {
// the core of answer is 2 lines below
var dummy = '?dummy=';
img.attr('src', img.attr('src').split(dummy)[0] + dummy + (new Date()).getTime());
// remove call on production
updateImgVisualizer();
};
// for display current img url in input
// for sandbox only!
var updateImgVisualizer = function() {
$('#img-url').val(img.attr('src'));
};
// bind img reload on btn click
$('.img-reloader').click(function() {
refreshImg(img);
});
// remove call on production
updateImgVisualizer();
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<img id="img" src="http://dummyimage.com/628x150/">
<p>
<label>
Current url of img:
<input id="img-url" type="text" readonly style="width:500px">
</label>
</p>
<p>
<button class="img-reloader">Refresh</button>
</p>

Answer 11

I may have to reload the image source several times. I found a solution with Lodash that works well for me:
$("#myimg").attr('src', _.split($("#myimg").attr('src'), '?', 1)[0] + '?t=' + _.now());
An existing timestamp will be truncated and replaced with a new one.

Answer 12

If you need a refresh of the exact URL and your browser has the image cached, you can use AJAX and a request header to force your browser to download a new copy (even if it isn't stale yet). Here's how you'd do that:
var img = $("#myimg");
var url = img.attr("src");
$.ajax({
url: url,
headers: { "Cache-Control": "no-cache" }
}).done(function(){
// Refresh is complete, assign the image again
img.attr("src", url);
});
Nothing else worked for me because while appending a token to the query string would download the new image, it didn't invalidate the image in the cache at the old URL so future requests would continue to show the old image. The old URL is the only one sent to the browser, and the server was directing the client to cache the image for longer than it should.
If this still doesn't refresh the image for you, see if this answer helps. For more information, here is documentation on the Cache-Control request header.

Answer 13

In the html:
foreach (var item in images) {
<Img src="#Url.Content(item.ImageUrl+"?"+DateTime.Now)" >
}

Answer 14

I simply do this in html:
<script>
$(document).load(function () {
d = new Date();
$('#<%= imgpreview.ClientID %>').attr('src','');
});
</script>
And reload the image in code behind like this:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
image.Src = "/image.jpg"; //url caming from database
}
}