仅运行一次功能。 &&在IE中不起作用

Question

此功能只能运行一次，该功能只能在Chrome和FF中运行。但是在IE中，您可以多次运行它。如何使它只能在IE中运行一次？

function topSect() {
  var mouseY = 0;
  var topValue = 10;
  var executed = false;

  window.addEventListener("mouseout", function(e) {
      mouseY = e.clientY;
      if (mouseY < topValue && !executed) {
        //do something here
        executed = true;
      }
    },
    false);
};

Answer 1

使用removeEventListener以确保仅一次触发了鼠标离开。

var mouseY = 0;
var topValue = 10;
var executed = false;

function mouseoutHandler(e){
  window.removeEventListener("mouseout", mouseoutHandler, false);
  mouseY = e.clientY;
  exectued = true;
  console.log(mouseY);
}

function topSect() {
  window.addEventListener("mouseout", mouseoutHandler, false);
};


topSect();