Javascript Optimization / Preloading / XLib / Whitespaces
Nov 30, 2005
Can anyone give me the 101 on optimizing javascript? Basically I've used a lot of javascript and DHTML and wanted to smooth my page out a little more.
I was testing my site, and the smooth sliding motion (THANKS MIKE FOSTER) that I thought was so so smooth was acting rather choppy. Turns out I had a couple other javascript heavy pages opened in another window and then *lightbulb* optimize your .js
So I know some basics about HTML and CSS opptimization, eg Tables=slow, CSS is there for a reason, limit style tags and js in HTML, elim white space etc. but i also read don't fiddle with javascript unless you know what you are doing. Well I don't, so here are a few:
How do browsers cache external js files?
several big external js files or many individual js files?
What about eliminating white space in .js will this cause problems?
Tips on preloading? (i'm doing a site on graphics so I'd rather put up a preloadpage hints?)
any articles or resources? best way to optimize/preload images?
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Mar 28, 2006
I have finally figured out how to make a call to an XML file using AJAX and then bringing it into the browser to manipulate with JavaScript. The only problem I'm having now is that I can't figure out how to remove the whitespaces between nodes so they won't show up as a childNode.
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Aug 13, 2007
is there a way in which I could optimize my code with
just one for loop (see code below). I've come across this issue a few
times now and haven't found a solution as yet.. As you can see from
the code below I'm reusing the same loop throughout three functions, I
basically see this as a waste. Is there a more efficient way where I
could use the for loop just the once. Code:
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May 15, 2011
I'm used to building objects in Visual Basic and I'm having difficulty simplifying this code into an object so I can just define and run about a dozen of them.
The code creates a button which changes on mouseover and on mouseclick. The button is a link to another page.
Also on mouseover the button slides to the right, giving a more intelligent feel for the user.
What are my options for streamlining this code so I can reduce the number of lines of code-clutter?
The code below is formatted properly.
PHP Code:
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Apr 14, 2011
I'm finding IE9 handles the preloading of images using the Image object differently to its earlier versions.For example:
This code in the <head>
Code:
<script type="text/javascript">
var picData = ['num1.jpg','num2.jpg','num2.jpg','num2.jpg'];
picO = new Array();
[code]....
Earlier versions of IE seem to work as FF4 does.It appears that the window.onload event in IE9 does not take into account if all the images have completed downloading via the above FOR loop whereas FF4 and the others do.
The workaround I am using is to preload the images in hidden <img>'s at the top of the <body> and then loading them into an Image object to get the jpg's actual width and height. This is working in IE9, FF4 and the other majors.
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Aug 18, 2004
You know how most Web pages load elements one-at-a-time? Well, I'd like to have my page appear all-at-once (all graphics, text, etc.).
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Apr 30, 2001
I'm using ie 5 and I was preloading these images for a rollover and I noticed the preloading wasn't working.
I looked at my code from all angles and couldn't figure it out - checked online examples on how to do it - same way I'm doing it.
Checked a different browser - worked fine.
So is there a security setting in IE that may disable preloading stuff? Or idoes my browser just need to be reinstalled?
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Jun 5, 2001
Is it possible to preload .js files the same way as pics (or any other way) ? The reason i ask is I have grabbed some nifty navigation code, but takes a little time to load first time.
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Oct 19, 2005
I´m using the following code to preload the hover images of my navigation:
Code:
menu_0101 = new Image();
menu_0101.src = "images/menu_0101_h.gif";
My question: When I enter the page the second time will the images be taken from the browser´s cache or from the server?
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Apr 14, 2011
I'm finding IE9 handles the preloading of images differently to IE8 and FF4 and the latest versions of other browsers.
In IE9 the preloading still works ok unless I want to use the width or height properties of the created Image object before the src of the new Image has been assigned to an <img>
For example:
This code in the <head>
Code:
outputs '0 0' in IE9 and '150 250' in FF4 and the latest versions of the major browsers. 150 and 250 are the actual width and height of mypic1.jpg
Earlier versions of IE seem to work as FF4 does.
It appears that the window.onload event in IE9 does not take into account if all the images have completed downloading via the above FOR loop whereas FF4 and the others do.
The workaround I am using is to preload the images in hidden <img>'s at the top of the <body> and then loading them into an Image object to get the jpg's actual width and height. This is working in IE9, FF4 and the other majors.
Have I missed or misunderstood something in the the way IE9 works?
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Aug 9, 2011
I am attempting to preload an array of images on my website so that they preload in order and only preload one at a time (the images are large and I want them to load in the order they will be viewed in.)So far I have this:
Code:
var images = new Array();
images[0]="website/users/user1/images/0001_000_808460.jpg"
images[1]="website/users/user1/images/0001_001_800872.jpg"
[code]....
This preloads the images all at once. I have yet to figure out a way so that "images[0]" loads first and completely before "images[1]" (and so on).
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Jul 23, 2005
Is this the correct way to preload an image...?
Var Image1 = new Image()
....And then when I'm ready to use the image I can do this...?
Button1.src=Image1.src
....Or am I just telling Button1 to use the same source path as Image1?
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Sep 14, 2005
I now have, in the header,
[Code]...
The above is in the first page where only the first image above, the before-and-after.gif image, is displayed. The rest are displayed in the second page linked to the first and are shown by using an array
[Code]...
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Oct 9, 2010
Is it possible to preload a single div with jquery? or simple Javascript?
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Aug 31, 2009
I have a function that changes the src of an image:
JavaScript Code:
function ChangeSRC(url_src)
{
document.getElementById("photo").src = url_src;
}
[code]....
Neither of these methods seem to work; especially in IE. Is there a better way to preload dynamic images?
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May 16, 2009
I'm working on an embedded system that I want to stream images from a webcam and having a world of problems.I originally started out using mime's multipart/x-mixed-replace to send the images to the browser and it worked well but IE has no support for it and it simply didnt work on slow connections.So i've changed to creating an image object and preloading it with JS but I cant get any onload functionality to work :crying: I want the page to preload a picture, display it, repeat with the next picture etc.
This is a rough version of what I have so far and it works while the timer is quite high >1sec, but just below that random images don't get displayed. With small delays, say 0.1sec the images are loaded but never displayed. why can't i get it to SHOW the image, THEN load the next one
PHP Code:
<script>
var image = new Image();
var tmr = -1;
[code]...
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Mar 14, 2009
I just spent 3 hours analyzing tons of lightboxes, image galleries, jQuery plugins. Now I'm a bit frustrated.I don't want a snazzy animation effect.I don't want a pre-made layout.This is what I want:On page load, 12-15 bigger images are preloaded into browser cache.Div#container contains a default image.When user clicks a thumbnail link, the corresponding (bigger) preloaded image shows inside #container.
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May 11, 2009
I'm trying to combine two scripts I found online to make a preloader for all the images in a folder. The javascript part works when you manually enter in a list of images, so I was trying to make a php array to get all the names of the images in one directory, then use that to list them. Here's what I tried:
<?php
function dirList ($directory)
{
[code]...
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Jun 13, 2003
I just thought this might be useful - short little pre-loading of images on webpage.
Code:
<body onload="preImages()">
<script>
function preImages(){
if (document.images){
aImgSrc = new Array("image1","image2","image3");
aImgLst = new Array ();
for(counter in aImgSrc){
aImgLst[counter] = new Image();
aImgLst[counter].src = "images/" + aImgSrc[counter] + ".jpg";
}}}
</script>
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Jul 6, 2011
I am developing a website for my budding photographer son, Tom, and I want to provide an gallery where the user clicks on a thumbnail and this displays a larger image. The only way I see that I can do this is to have a link on the thumbnail to load the page again passing the image name or id to the page using a query string and processing this using PHP. If I preload all of the larger images when the site first loads will these images be available in the cache for other pages.Another way is to hover the thumbnails and display the larger image but I need to find a way to keep the image displayed until the user hovers over another thumbnail.
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Mar 16, 2005
I issue a css rule for my table that will contain the masthead thus:
table.banner{background-image:url(background.gif);background-repeat:no-repeat;}
Afterwhich i preloaded the background image using javascript thus:
<script>
banner=new Array();
banner[1]=new Image();
banner[1].src="background.gif";
</script>
when i tested this script i didn't notice that the background image got pre loaded pls am i doing anything wrong?
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Dec 11, 2005
The two pages for preloading below seemed to preload images IF I used an absolute path but they don't preload the images if I just used relative paths like the ones below.
Give it a try. The two pages below using relative paths won't work. Then try changing the paths of the images in both pages to use absolute path(with http://) which will work.
But I want to use relative paths. What can be done? Other than inserting 1x1 size of the images I want to preload. Code:
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May 1, 2010
I have a page where there are 4 images that are loaded as a div background via css file.
When I try to use javascript to preload them it just does not look like its pre loading them.
I tried doing the following but the images don't pre loaded. They appear one after another.
Code:
<SCRIPT language="JavaScript">
<!--
pic1= new Image(100,25);
pic1.src="http://someplace.com/image1.gif";
//-->
</SCRIPT>
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Feb 16, 2010
I am trying to preload over 300 small images. I am using a local developement server at this point and testing in IE. As the user interacts with the page many different images will be appear and dissapper for them. It needs to be smooth. I was noticing that the status bar at the bottom of IE keeps saying the images are being loaded. So I thought I would try preloading the images. After implementing the following code, the IE status bar seems to still show that the images are loading each time and I havent noticed any improvement in load times. Could it be that the images are not really being preloaded? Here is the code I am using to preload (it is triggered by onload in the body tag:
imageObj = new Image(width, height);
imageObj.src = "images/pp1234.png"
my actual code repeats the second line many times in a loop with different image names, but this is the most basic for of my code and it results in the same problem. Are there known issues with IE and preloading?
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Oct 15, 2005
I've inherited responsibility for our church's website. It has a
sizeable main menu, which uses mouseover image swaps. These images use a
pre-load script but the script is only included in the index.html page. My
javascript knowledge is weak, but it seems to me if a viewer arrives first
at page12.html, he gets no benefit of the preload script. My quandry -
Should I include the preload script on every page, or would this force each
of these images to download again everytime a viewer moves to a different
web page, thereby gumming up the whole works? If I don't add it to every
page, the viewer who enters thru a backdoor has a sluggish menu, right?
If the right approach is to include it on every page, can I do this with an
external js file? Will I need to call this file, or will it work just by
including the js statement in the <head> section:
<SCRIPT LANGUAGE="JavaScript" SRC="preloadscript.js"></SCRIPT>
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Sep 25, 2006
I currently have a Javascript application that randomizes about 200
images. The problem is that the images preload, which causes the entire
site to not come up until all the images are loaded. I'd like to find a
Javascript application that can load images as they are randomly
chosen. In addition, I'm trying to figure out how to not display the
same image more than once; or at least until after the 200 have been
displayed, then create a new randomization of the 200 images.
Let me know if anyone knows how to do this or can point me to code that
is able to do what I'm looking for.
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