$ git clone git://github.com/mooz/js2-mode.git
$ cd js2-mode
$ emacs --batch --eval '(byte-compile-file "js2-mode.el")'

(autoload 'js2-mode "js2-mode" nil t)
(add-to-list 'auto-mode-alist '("\\.js$" . js2-mode))

let {a, b}       = {a: 10, b: 20}; // Abbreviated   (Not supported in original js2-mode.el)
let {a: a, b: b} = {a: 10, b: 20}; // Same as above (Supported in original js2-mode.el)

(function ({responseText}) { /* */ })(xhr); // As the argument of function

let worker = {
    get age() 20,
    get sex() "male",
    fire: function () _fire()
};

if (foo)
    return foo;
else if (bar)
return bar;      // here

if (foo)
    return foo;
else if (bar)
    return bar;  // fixed