Converting user input string to regular expression

Question

I am designing a regular expression tester in HTML and JavaScript. The user will enter a regex, a string, and choose the function they want to test with (e.g. search, match,

Answer 1

Thanks to earlier answers, this blocks serves well as a general purpose solution for applying a configurable string into a RegEx .. for filtering text:

var permittedChars = '^a-z0-9 _,.?!@+<>';
permittedChars = '[' + permittedChars + ']';

var flags = 'gi';
var strFilterRegEx = new RegExp(permittedChars, flags);

log.debug ('strFilterRegEx: ' + strFilterRegEx);

strVal = strVal.replace(strFilterRegEx, '');
// this replaces hard code solt:
// strVal = strVal.replace(/[^a-z0-9 _,.?!@+]/ig, '');