javascript regex to validate alphanumeric character in an input field [duplicate]

Question

I want to check whether my userid is having any special character apart from alphanumeric characters (a-z,A-Z,0-9). The below regex is failing...what would be the correct way?

var testStr = '3278|3278.3000.2506.60200000.1100.000.0000.0||703"68*[70"8'; var splitTeststr = testStr.split('|'); alert(splitTeststr[0]); /* alert('Length of splitStr is : ' +splitTeststr.length); */ if (splitTeststr.length == 4) { var userId = splitTeststr[3].trim(); alert('userId before removing junk : ' +userId); var letterNumber = /^[0-9a-zA-Z]+$/; if((userId.match(letterNumber))){ alert('UserId contains junk : ' +userId); }else{ alert('Userid is fine'); } }

It seems that your regex is correct but your condition is reversed — Axnyff
– Axnyff, Commented Jul 29, 2020 at 11:03
This is not about you, but I wonder why in 2020 people keep using var and alert. This is so recurring on SO that I'm starting wondering if they're all from the same source — Christian Vincenzo Traina
– Christian Vincenzo Traina, Commented Jul 29, 2020 at 11:03
@CristianTraìna- Our legacy application will support in this way only. Oracle product :) — Cris-123
– Cris-123, Commented Jul 29, 2020 at 11:13

Greedo · Accepted Answer · 2020-07-29 11:14:59Z

There is an issue in your regex, the correct one is /[^0-9a-zA-Z]/:

function testUserId(userId){ console.log('userId before removing junk : ' +userId); var letterNumber = /[^0-9a-zA-Z]/; if((userId.match(letterNumber))){ console.log('UserId contains junk : ' +userId); }else{ console.log('Userid is fine'); } } // letter and numbers testUserId("34293483209jfeoiAAAAsojf"); // numbers testUserId("1234"); // letters testUserId("aaaBBBBB"); // rejected testUserId("aa!aBBB!..BB");

@Greedo- Thanks. Yeah...i too just figured it out. Cool buddy.

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