javascript regular expression remove non alphanumeric code example

Example 1: remove non alphanumeric characters javascript

input.replace(/\W/g, '') //doesnt include underscores


input.replace(/[^0-9a-z]/gi, '') //removes underscores too

Example 2: javascript regular expression for alphanumeric

/^[a-z0-9]+$/i

^         Start of string
[a-z0-9]  a or b or c or ... z or 0 or 1 or ... 9
+         one or more times (change to * to allow empty string)
$         end of string    
/i        case-insensitive