Question

var regEx = new RegExp("/[0-9]/");
var test = 'TREE'
alert(test.match(regEx));

or

var regEx = new RegExp("/[0-9]/");
var test = '1234'
alert(test.match(regEx));

Why do they return null?

Am i missing something here?

(Ok, the debate mentally drained me last night)

Answer 1

When you are using new RegExp, you don’t need the delimiters (/).

var regEx = new RegExp("[0-9]");
var test = '1234'
alert(test.match(regEx));

You only need the slashes if you are using a regex literal (which I prefer using to new RegExp).

var regEx = /[0-9]/;
var test = '1234'
alert(test.match(regEx));