为什么我点击预览，角色却无法出现

Creator 2.x
#1

代码如下`// Learn cc.Class:
// - https://docs.cocos.com/creator/manual/en/scripting/class.html
// Learn Attribute:
// - https://docs.cocos.com/creator/manual/en/scripting/reference/attributes.html
// Learn life-cycle callbacks:
// - https://docs.cocos.com/creator/manual/en/scripting/life-cycle-callbacks.html

cc.Class({
extends: cc.Component,

properties: {
    // foo: {
    //     // ATTRIBUTES:
    //     default: null,        // The default value will be used only when the component attaching
    //                           // to a node for the first time
    //     type: cc.SpriteFrame, // optional, default is typeof default
    //     serializable: true,   // optional, default is true
    // },
    // bar: {
    //     get () {
    //         return this._bar;
    //     },
    //     set (value) {
    //         this._bar = value;
    //     }
    // },
},
//player.js 
  //player编写
    properties: {
      //角色初始化变量定义
      //角色跳跃高度
      jumpHeight:0,
      //角色跳跃持续时间
      jumpDuration:0,
      //角色最大速度，定义最大
      maxMoveSpeed:0,
      //加速度
      accel:0,
     },


     runJumpAction (){
        //jump up
        var jumpUp = cc.tween().by (this.jumpDuration ,{y:this.jumpDuration },{easing :'sindOut'})
        //jump down
        var jumpDown = cc.tween().by (this.jumpDuration,{y:-this.jumpDuration},{easing :'sindIn'})
        
        //创建缓动系统，先跳跃，后下落
        var tween = cc.tween().sequence(jumpUp,jumpDown)
        //重复动作
        return cc.tween.repeatForever(tween)
     },   
     
     onLoad: function () {
        var jumpAction = this.runJumpAction();
        cc.tween(this.node).then(jumpAction).start()
    },

    runJumpAction: function () {
        //...
    },

    onKeyDown (event) {
        // set a flag when key pressed
        switch(event.keyCode) {
            case cc.macro.KEY.a:
                this.accLeft = true;
                break;
            case cc.macro.KEY.d:
                this.accRight = true;
                break;
        }
    },

    onKeyUp (event) {
        // unset a flag when key released
        switch(event.keyCode) {
            case cc.macro.KEY.a:
                this.accLeft = false;
                break;
            case cc.macro.KEY.d:
                this.accRight = false;
                break;
        }
    },

    onLoad: function () {
        // 初始化跳跃动作
        var jumpAction = this.runJumpAction();
        cc.tween(this.node).then(jumpAction).start()

        // 加速度方向开关
        this.accLeft = false;
        this.accRight = false;
        // 主角当前水平方向速度
        this.xSpeed = 0;

        // 初始化键盘输入监听
        cc.systemEvent.on(cc.SystemEvent.EventType.KEY_DOWN, this.onKeyDown, this);
        cc.systemEvent.on(cc.SystemEvent.EventType.KEY_UP, this.onKeyUp, this);   
    },

    onDestroy () {
        // 取消键盘输入监听
        cc.systemEvent.off(cc.SystemEvent.EventType.KEY_DOWN, this.onKeyDown, this);
        cc.systemEvent.off(cc.SystemEvent.EventType.KEY_UP, this.onKeyUp, this);
    },

    update: function (dt) {
        // 根据当前加速度方向每帧更新速度
        if (this.accLeft) {
            this.xSpeed -= this.accel * dt;
        }
        else if (this.accRight) {
            this.xSpeed += this.accel * dt;
        }

        // 限制主角的速度不能超过最大值
        if (Math.abs(this.xSpeed) > this.maxMoveSpeed) {
            // if speed reach limit, use max speed with current direction
            this.xSpeed = this.maxMoveSpeed * this.xSpeed / Math.abs(this.xSpeed);
        }

        // 根据当前速度更新主角的位置
        this.node.x += this.xSpeed * dt;
    },


// LIFE-CYCLE CALLBACKS:

// onLoad () {},


// update (dt) {},

});

可是我的角色却运行不了，且无法显示`