Give a regex, get a robust predicate function that tests it against a string. This will work even if RegExp.prototype is altered later.

npm install --save safe-regex-test

var regexTester = require('safe-regex-test');
var assert = require('assert');

var tester = regexTester(/a/);
assert.ok(tester('a'));
assert.strictEqual(tester('b'), false);

Simply clone the repo, npm install, and run npm test