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I have a regular expression and I want to check this regular expression is valid or not(correct format).

I try to use this code as below to check but it run not good

var regExp = new RegExp();
regExp.compile("^[\d\-]{0,64}"); => check OK.
regExp.compile("[[\d\-]{0,64}"); => check Not Good.

How to check my regular expression is correct format or not? Please help me handle this case.

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  • 1
    Need to escape the second [ to match it literally Commented Nov 11, 2015 at 4:28
  • 1
    Are you asking for a way to check if your JavaScript syntax be correct, or do you want a way to check if the regex be logically correct (meaning it matches what you want to match) ? Commented Nov 11, 2015 at 4:28
  • Use try/catch around the regexp definition. Commented Nov 11, 2015 at 4:30
  • Seems slightly odd to mark a question as a duplicate of a question which was closed. Commented Nov 14, 2015 at 7:10

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Use try/catch to catch the error when creating the regexp.

Object.defineProperty(RegExp, 'compile', {
    value: function (regexp) {
        try {
            new RegExp(regexp);
            return "OK";
        } catch(e) {
            return "Not Good";
        }
    }
});

Some might object to adding methods to the RegExp object. In the above, I've adopted your proposed interface implementing this as RegExp.compile.

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4 Comments

Quick Q: Why not defining property directly on RegExp proto? Any advantage of using Object.def...
new RegExp("[[\d-]{0,64}") return error ?
@guest271314 This will not return error. This will only check if the passed string can be complied to regex. And for your example, the regex is compiled to /[[d-]{0,64}/ which is valid regex, but will not match what OP/you might expect.
@Tushar There is no way to check if a regexp does what the OP expects, because the computer has no way to know what he expects.

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