Function cancellable

01.GettingStarted/js/vue.js:368–378

* Make a cancellable version of an async callback. * * @param {Function} fn * @return {Function}

(fn)

   */

  function cancellable(fn) {
    var cb = function cb() {
      if (!cb.cancelled) {
        return fn.apply(this, arguments);
      }
    };
    cb.cancel = function () {
      cb.cancelled = true;
    };
    return cb;
  }

  /**
   * Check if two values are loosely equal - that is,