第一次点击后，javascript禁用事件监听器

Question

如何禁用此事件侦听器以便它只触发一次？

document.getElementById('element').ontouchmove = function (e) 
{   
  DISABLE HERE
  do something that should only happen once
};

Answer 1

document.getElementById('element').ontouchmove = function (e) {   
  this.ontouchmove = null;

  // Do something here.
};

Answer 2

首次执行后将布尔值设置为false，每次运行函数前都会检查它：

var doTouchEvent = true;
document.getElementById('element').ontouchmove = function (e) 
{   
   if(doTouchEvent){
      DISABLE HERE
      do something that should only happen once


      doTouchEvent = false;
   }
};