Alphanumeric, dash and underscore but no spaces regular expression check JavaScript
JavascriptRegexJavascript Problem Overview
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\-\_]$/;
var check = "checkme";
if (check.search(regexp) == -1)
{ alert('invalid'); }
else
{ alert('valid'); }
Javascript Solutions
Solution 1 - Javascript
> However, the code below allows spaces.
No, it doesn't. However, it will only match on input with a length of 1. For inputs with a length greater than or equal to 1, you need a + following the character class:
var regexp = /^[a-zA-Z0-9-_]+$/;
var check = "checkme";
if (check.search(regexp) === -1)
{ alert('invalid'); }
else
{ alert('valid'); }
Note that neither the - (in this instance) nor the _ need escaping.
Solution 2 - Javascript
This is the most concise syntax I could find for a regex expression to be used for this check:
const regex = /^[\w-]+$/;
Solution 3 - Javascript
You shouldn't use String.match but RegExp.prototype.test (i.e. /abc/.test("abcd")) instead of String.search() if you're only interested in a boolean value. You also need to repeat your character class as explained in the answer by Andy E:
var regexp = /^[a-zA-Z0-9-_]+$/;
Solution 4 - Javascript
Got stupid error. So post here, if anyone find it useful
[-\._]- means hyphen, dot and underscore[\.-_]- means all signs in range from dot to underscore
Solution 5 - Javascript
Try this
"[A-Za-z0-9_-]+"
Should allow underscores and hyphens
Solution 6 - Javascript
Don't escape the underscore. Might be causing some whackness.
Solution 7 - Javascript
try this one, it is working fine for me.
"^([a-zA-Z])[a-zA-Z0-9-_]*$"