Alphanumeric, dash and underscore but no spaces regular expression check JavaScript

Question

Trying to check input against a regular expression.

The field should only allow alphanumeric characters, dashes and underscores and should NOT allow spaces.

However, the code below allows spaces.

What am I missing?

var regexp = /^[a-zA-Z0-9\-\_]$/; var check = "checkme"; if (check.search(regexp) == -1)     { alert('invalid'); } else     { alert('valid'); } 

Answer 1

However, the code below allows spaces.

No, it doesn't. However, it will only match on input with a length of 1. For inputs with a length greater than or equal to 1, you need a + following the character class:

var regexp = /^[a-zA-Z0-9-_]+$/; var check = "checkme"; if (check.search(regexp) === -1)     { alert('invalid'); } else     { alert('valid'); } 

Note that neither the - (in this instance) nor the _ need escaping.

Answer 2

You shouldn't use String.match but RegExp.prototype.test (i.e. /abc/.test("abcd")) instead of String.search() if you're only interested in a boolean value. You also need to repeat your character class as explained in the answer by Andy E:

var regexp = /^[a-zA-Z0-9-_]+$/;