/**
 * 惯性原理:
 * 产生的速度 = 移动距离 / 移动时间
 * 距离 = 松开的坐标 - 上次的坐标  (距离差)
 * 时间 = 松开的时间 - 按下的时间  (时间差)
 * */

var dargFun = {
    dargDom:null,//惯性滑动的DOM区域
    startX:0,1)">开始偏移的X
    startY:0,1)">开始偏移的Y
    clientX:0,clientY:0保存的X偏移
    translateY:0,1)">保存的Y偏移
    maxWidth:0,1)">滑动的最大宽度
    maxHeight:0,1)">滑动的最大高度
    startTime:0,1)">记录初始按下时间
    init:function(config){
        this.dargDom = document.querySelector(config.dargDom);
        this.maxWidth = this.dargDom.offsetWidth;
        this.maxHeight = .dargDom.offsetHeight;
        
        this.dargDom.addEventListener('touchstart',(event)=>{
            event.stopPropagation(); 停止事件传播
            this.clientX = event.changedTouches[0].clientX;
            this.clientY = event.changedTouches[0].clientY;
            this.dargDom.style.WebkitTransition = this.dargDom.style.transition = '';
            this.startX = .translateX;
            this.startY = .translateY;
            this.startTime = Date.now();
        },false);
        
        this.dargDom.addEventListener('touchmove',1)">{
            if(document.documentElement.scrollTop >= this.dargDom.scrollHeight - .dargDom.clientHeight){
                
            }else{
                return;
            }
        
            event.stopPropagation(); this.translateX = event.changedTouches[0].clientX - this.clientX + .startX;
            this.translateY = event.changedTouches[0].clientY - this.clientY + .startY;
            if(this.translateY > 0 ){ 拖动系数. 拉力的感觉
                this.translateY *= 0.4;
            }else if( this.translateY < -(.dargDom.clientHeight)){ 
                this.translateY = (event.changedTouches[0].clientY - this.clientY) * 0.4 + .startY;
            }
            this.animate(.translateY);
        },1)">this.dargDom.addEventListener('touchend',1)">var distanceY = event.changedTouches[0].clientY - .clientY,timeDis = Date.now() - this.startTime,1)">时间差
            speed = (distanceY / timeDis) * 100;
            
             惯性
            this.translateY += speed;
    
            this.translateY  = 0 添加贝塞尔曲线
            this.dargDom.style.transition = 'transform 500ms cubic-bezier(0.1,0.57,0.1,1)'.translateY);
        
        },1)">);
        
    },animate:(y){
        this.dargDom.style.WebkitTransform = this.dargDom.style.transform = 'translateY('+y+'px)';
    }
}

export default dargFun;

dragFun.init({
    dargDom:'#contractContanier'
});