function test(x) { var _x; _x = x; var F = function F() { "use strict"; babelHelpers.classCallCheck(this, F); babelHelpers.defineProperty(this, _x, 1); }; x = 'deadbeef'; expect(new F().foo).toBe(1); x = 'wrong'; expect(new F().foo).toBe(1); } test('foo');