August 2012
Beginner
583 pages
16h 1m
English
Content preview from Learning PHP, MySQL, JavaScript, and CSS, 2nd EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Validating User Input with JavaScript
JavaScript validation should be considered an assistance more to your users than to your websites because, as I have already stressed many times, you cannot trust any data submitted to your server, even if it has supposedly been validated with JavaScript. This is because hackers can quite easily simulate your web forms and submit any data of their choosing.
Another reason you cannot rely on JavaScript to perform all your input validation is that some users disable JavaScript, or use browsers that don’t support it.
So, the best types of validation to do in JavaScript are checking that fields have content if they are not to be left empty, ensuring that email addresses conform to the proper format, and ensuring that values entered are within expected bounds.
The validate.html Document (Part One)
Let’s start with a general signup form, common on most sites that offer memberships or registered users. The inputs being requested will be forename, surname, username, password, age, and email address. Example 16-1 provides a good template for such a form.
Example 16-1. A form with JavaScript validation (part one)
<html><head><title>An Example Form</title>
<style>.signup { border: 1px solid #999999;
font: normal 14px helvetica; color:#444444; }</style>
<script>
function validate(form) {
fail = validateForename(form.forename.value)
fail += validateSurname(form.surname.value)
fail += validateUsername(form.username.value)
fail += validatePassword(form.password.value) ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.