src/third_party/mozjs-45/js/src/jit-test/tests/basic/testDateNow.js

function testDateNow() {
    // Accessing global.Date for the first time will change the global shape,
    // so do it before the loop starts; otherwise we have to loop an extra time
    // to pick things up.
    var time = Date.now();
    for (var j = 0; j < 9; ++j)
        time = Date.now();
    return "ok";
}
assertEq(testDateNow(), "ok");