Function step

06.Router/basic/js/vue-router.js:1501–1509

(index)

      var transition = this;
      step(0);
      function step(index) {
        if (index >= queue.length) {
          cb();
        } else {
          fn(queue[index], transition, function () {
            step(index + 1);
          });
        }
      }
    };

    /**