Javascript Validate alphanumeric with minimum text length

Question

This script is working properly to validate alphanumeric without spaces. But how will i also include that the minimum length should be at least 3 chars?

var re = /^[A-Za-z0-9']+$/; // Check input if (re.test(document.getElementById(x).value)) { // Style green document.getElementById(x).style.background = '#ccffcc'; // Hide error prompt document.getElementById(x + 'Error').style.display = "none"; return true; } else { // Style red document.getElementById(x).style.background = '#e35152'; // Show error prompt document.getElementById(x + 'Error').style.display = "block"; return false; }

Thanks in advance.

Mr. Polywhirl · Accepted Answer · 2014-09-12 10:12:11Z

2

Have you tried?

/^[A-Za-z0-9']{3,}$/; . (Zero or more items) + (One or more items) {n} (Exactly n items) {n,m} (Between n and m items where n < m)

edited Sep 12, 2014 at 10:12

answered Sep 11, 2014 at 11:43

Mr. Polywhirl

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1 Comment

user3524542 Over a year ago

\d means digits, it is equivalent to [0-9], and \w means [a-zA-Z0-9_]. Pay attention that \w includes underscore too.

Guffa · Accepted Answer · 2014-09-11 11:43:28Z

Change the + quantifier (which means one or more times) to {3,} (which means three or more times):

var re = /^[A-Za-z0-9']{3,}$/;

OhleC · Accepted Answer · 2014-09-11 11:50:07Z

You could use an appropriate quantifier in your regular expression:

var re = /^[A-Za-z0-9']{3,}$/;

Or refactor your validation into its own function, which would be more maintainable:

var isValid = function(value) { var re = /^[A-Za-z0-9']+$/; if (!re.test(value)) { return false; } if (value.length < 3) { return false; } // further tests could go here return true }

Barmar · Accepted Answer · 2014-09-11 11:43:54Z

Change the regexp to:

var re = /^[A-Za-z0-9']{3,}$/;

The quantifier {min,max} means from min to max repetitions. If you leave either of them out, it means that end is unlimited, so {3,} means at least 3.

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