Jsb main.js loadJs slow, how to add loading scene?

cocos2d-x JavaScript
1

platform cocos2d-x jsb (native), not html5

i game have 700+ js files, in main.js, it will use cc.game.loadJS to load js files, such as

          cc.loader.loadJs(["src/jsFiles.js"], function() {
                cc.loader.loadJs(jsFiles, function() {
                    var scene = LoginScene.create();
                    cc.director.runScene(scene);
                });
            });
```
but, it will cost a lot of time in require js file, even use 10s or more. 

i have two question.
q1:why require some js files use much more time?  my js files haven't new any object, all of them are class which extend from cc.Class and some global macro define. such as
#### a.js
```
var MySprite = cc.Sprite.extend({
.....
})
```

#### b.js
```
var matchConst = matchConst || {};
matchConst.MATCH_TYPE = 0;
.....
```

q2:how to add loading scene when require files?
2

any one can help