Javascript regular expression check flag support

Question

In javascript, how can i check if a certain flag in regular expression is supported or not ?
For some new flags, i keep getting "invalid regular expression flag" error.

Answer 1

You can use RegExp constructor. It prevents syntax error and allows you to optionally detect and use that flag without aborting execution.

function isRegExpFlagSupported() {
    try {
        var regexp = new RegExp("foo.*bar", "s");
        return true;
    } catch (ex) {
        return false;
    }
}

If you execute it outside try-catch block like this,

var regexp = new RegExp("foo.*bar", "s");

it will throw error "invalid regular expression flag s".

Answer 2

If you don't know the composition of the regex then can convert it into a string and use a regex to capture the letters after the last / character. Like /test/gi.toString().match(/\\w*$/); // <- ["gi"] /test/gi.toString().match(/\\w*$/); // <- ["gi"]