Check if string is a prefix of a Javascript RegExp

Question

In Javascript I have defined a regular expression and now a user is typing in a string. I want to tell him if his string still could match the RegExp if he continues typing

Answer 1

First you define your regular expression as: var re = new RegExp(/^(regexp here)$/);

on the onKeypress event, you check the regexp like this:

text.match(regexp) - where the text is the string entered.

Is this clear?