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Useful Scripts

Chapter 8: Forms and Regular Expressions

Contents:

Validating an Email Address with Regular Expressions
Validating a File Name
Extracting Strings
Formatting Strings
Formatting and Sorting Strings
Formatting and Validating Strings
Replacing Elements using Regular Expressions

Return to Chapter 8

To use this script on your own page, click in the text area below, select all, and copy to grab the script. Then, just paste into your own page — and you're done.

Validating a File Name

See it run: Validating a File Name

Script 8.3

This JavaScript asks for an image location and, if it passes the validation, displays the image on the page.

window.onload = initForms;

function initForms() {
	for (var i=0; i< document.forms.length; i++) {
		document.forms[i].onsubmit = function() {return validForm();}
	}
}

function validForm() {
	var allGood = true;
	var allTags = document.getElementsByTagName("*");

for (var i=0; i<allTags.length; i++) {
		if (!validTag(allTags[i])) {
			allGood = false;
		}
	}
	return false;

function validTag(thisTag) {
		var outClass = "";
		var allClasses = thisTag.className.split(" ");
	
		for (var j=0; j<allClasses.length; j++) {
			outClass += validBasedOnClass(allClasses[j]) + " ";
		}
	
		thisTag.className = outClass;
	
		if (outClass.indexOf("invalid") > -1) {
			invalidLabel(thisTag.parentNode);
			thisTag.focus();
			if (thisTag.nodeName == "INPUT") {
				thisTag.select();
			}
			return false;
		}
		return true;
		
		function validBasedOnClass(thisClass) {
			var classBack = "";
		
			switch(thisClass) {
				case "":
				case "invalid":
					break;
				case "imgURL":
					if (allGood && !imgURL(thisTag.value)) classBack = "invalid ";
				default:
					classBack += thisClass;
			}
			return classBack;
		}
				
		function imgURL(newURL) {
			var re = /^(file|http):\/\/\S+\/\S+\.(gif|jpg)$/i;

if (re.test(newURL)) {
				document.getElementById("chgImg").src = newURL;
				return true;
			}
			return false;
		}
		
		function invalidLabel(parentTag) {
			if (parentTag.nodeName == "LABEL") {
				parentTag.className += " invalid";
			}
		}
	}
}