I have watched a couple videos on JS where the presenter mentioned caching a variable but I didn't see them do anything in the code that would cache it beyond normal assignments. When i think of cache i think of something stored in local memory in which case aren't all js variables cached by definition.When you cache a variable in javascript what or you doing to it?EDIT:I have heard the term in several but the only one that comes to mind is Writing Modular Javascript - Tutorial. Which i just watched last night. I didn't post it because you have to pay to view and I hate feeling liking i am plugging a pay service on stackexchange.
Terminology - Cache (Javascript)
javascript;terminology
From this tutorial on efficient javascript:One of the best kept secrets to boosting script performance is to  cache your objects. Often times, your script will repeatedly access a  certain object, as in the following demonstration:<script type=text/javascript>for (i=0;i<document.images.length;i++)document.images[i].src=blank.gif</script>In the above, the object document.images is what's accessed multiple  times. The code to realizing it is inefficient, since the browser must  dynamically look up document.images twice during each loop (once to  see if i<document.images, and the other, to access and change the  image's src). If you have 10 images on the page, for example, that's  20 calls to the Images object right there. Excessive calls to  JavaScript objects can wear down the browser, not to mention your  computer's memory.The term cache your object means storing a repeatedly access object  inside a user defined variable, and using that variable instead in  subsequent references to the object. The performance improvement can  be significant. Here's a modified version of the initial script using  object caching:<script type=text/javascript>var theimages=document.imagesfor (i=0;i<theimages.length;i++)theimages[i].src=blank.gif</script>Not only is the number of times document.images[] is referenced cut in  half with the above, but for each time it is referenced, the browser  doesn't have to go through document.images first, but goes straight to  its containing array.Remember to use object caching when calling highly nested DHTML  objects, like document.all.myobject, or document.layers.firstlayer  etc.andsome JavaScript objects are less forgiving on the browser than others.  While recognizing exactly which isn't easy (and isn't the goal here),  just becoming aware of this fact is important.Take, for example, these two properties:-object.innerText //IE only-object.innerHTMLDid you know that the second property demands multiple times the  system resources to call than the first? If all you're changing is the  textual content of a <div> or <span> and in IE only, innerText would  definitely be the more efficient choice. Another example are the CSS  properties display and visibility; the former is significantly  more expensive than the later.With JavaScript object caching, the number of lookups is cutdown, since the object reference is held within the variable - potentially improving performance and memory usage. 