Feedback: irt.org FAQ Knowledge Base Q52

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irt.org FAQ Knowledge Base Q52

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Legal

Worth:
Worth reading

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Too short

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Just right

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You can also use the Image() object to test for the existence of a generic image (or any number of images) without ever displaying them on the page:

function testImage(URL)
{
var tester=new Image();
tester.onLoad=isGood;
tester.onError=isBad;
tester.src=URL;
}

function isGood()
{
alert('That image exists!');
}

function isBad()
{
alert('That image does no exist!');
}

This can be useful if, for example, the user must specify an image and you want to check whether it exists before submitting the form.

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Worth reading

Comments:
This solution dosn't seem to do it in MSIE, do you know a way to do it?

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Very worth reading

Length:
Too long

Technical:
Too technical

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With regard to my previous comment, this code only seems to work in Netscape 4. It no longer runs in Netscape 6, or in IE.

Worth:
Very worth reading

Length:
Just right

Technical:
Just right

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image.onLoad works for Netscape but for IE (at least for 5.5) you need to use image.onload (lowercase).

Comments:
How could this be used to display an alternate graphic image if the specified image in a <img> tag doesn't exits? Assume that a standard image will be loaded for the alternate image.

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Technical:
Just right

Comments:
An another way to do this...

function ImageTest(URL) {
var
MyImage = new Image();
I = 0;

MyImage.onerror = DoesntExists;
MyImage.src = URL;

if(I > 0){
return('<your another picture link>');
}

function DoesntExists(){
I++;
}

return(URL);
}

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Comments:
onerror somehow doesn't work with some browsers. Wonder if there's a way to check if there was an error in onload instead...