Does 'new Image()' allow for use of cache (JavaScript)

Question

If I use new Image() to load up an image in JavaScript, will it use a cached version if possible, or will it always load up a fresh copy?

var imgObj = new Image();
imgObj.src = 'http://...';
imgObj.onload = function (loadedImg) { }

I would setup the onload prior though. IIRC there are some strange Opera quirks with at least onerror and posting events synchronously vs. async. My memory fails though. — user166390
– user166390, Commented Oct 19, 2010 at 19:31
If you don't want to have it cached, add some random parameters to the source value, like: 'image.jpg?random=' + new Date().getTime() — Harmen
– Harmen, Commented Oct 19, 2010 at 19:31

gblazex · Accepted Answer · 2010-10-19 19:33:50Z

8

One thing to note is that if you want onload to always happen (even when it's in cache) you should define onload before src.

var imgObj = new Image();
imgObj.onload = function (loadedImg) { }
imgObj.src = 'http://...';

answered Oct 19, 2010 at 19:33

gblazex

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Comments

Nick Craver · Accepted Answer · 2010-10-19 19:27:28Z

7

It'll load from cache if it's there, the same way a <img> in your markup would.

answered Oct 19, 2010 at 19:27

Nick Craver

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(Or perhaps not load from cache-- those pesky misconfigured servers!)

Well, he is close to century of bronze medals.

Robusto · Accepted Answer · 2010-10-19 19:31:25Z

2

You can force a reload by adding a bogus query string argument. If your statement assigning a URL to the src property of the image is

imgObj.src = 'http://www.mySite.com/images/anImage.png';

you could render it as

imgObj.src = 'http://www.mySite.com/images/anImage.png?foo=0';

Just understand that on subsequent loads it will still use the cached copy unless you change the query string argument.

answered Oct 19, 2010 at 19:31

Robusto

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