Codezwiz >> Forums >> Javascript Help >> Checking if forms contain a certain string

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I'm trying to verify that a form field contains gif, jpg or png i and what i've got does check, however it verifies that the field ONLY contains one of those. If anything else...like the rest of the URL to the image is in the field it returns the alert.

function imagecheck(){
var string1=document.validation.image.value
if (string1.indexOf("gif")==0 || string1.indexOf("jpg")==0 || string1.indexOf("png")==0){
}
else{
alert("Only gif, jpg and png images are allowed!")
document.validation.image.focus()
}
}

I keep trying to grasp what your saying, but could we get an example?

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In the emailer for the Link Exchange I made that you saw in another post, there's a field where you input the link to your image. I am trying to make a javascript function that will check that field for the string gif, jpg or png to help make sure they put an image in. I am also hoping to come up with one that checks the structure of a URL.
For now I could start em off on the right track by giving those fields a value of [ Register or login to view links on this board. ] but it would be nice to mistake proof those fields.