regex in form code example

Example 1: using regex in javascript

//Adding '/' around regex
var regex = /\s/g;
//or using RegExp
var regex = new RegExp("\s", "g");

Example 2: regex on input

<form>
 <label for="username">Username <i>(letters and numbers only, no  punctuation or special characters)</i></label><br>
 <input name="username" id="username" pattern="[A-Za-z0-9]+">
</form>