How to check if the input string is a valid Regular expression?

Question

How do you check, in JavaScript, if a string is a proper regular expression that will compile?

For example, when you execute the following javascript, it produces a

Answer 1

You can use try/catch and the RegExp constructor:

var isValid = true;
try {
    new RegExp("the_regex_to_test_goes_here");
} catch(e) {
    isValid = false;
}

if(!isValid) alert("Invalid regular expression");