tachStart(item) //执行函数function tachStart(target) {    var time = null;     target.addEventListener("touchstart",function(){ //手指触摸执行        time = setTimeout(handler,800)    });    target.addEventListener("touchend",function(){ //手指离开执行        clearTimeout(time);     })}function handler(){  //长按    console.log("你长按了我")}