js简单鼠标手势

var mousePressedEventList = [];
function myFunction(e) {
  if (e.buttons == 1 || e.buttons == 2) {
    //按住左键
    mousePressedEventList.push(e);
  } else if (e.buttons == 0) {
    //释放的时候
    if (mousePressedEventList.length > 3) {
      firstPointY = mousePressedEventList[0].clientY;
      lastMouseEvent = mousePressedEventList[mousePressedEventList.length - 1];
      lastPointY = lastMouseEvent.clientY;

      if ((firstPointY > lastPointY) &&( lastMouseEvent.buttons==2)){
        //右键上划的情况
        window.scrollTo(0, 0); //回到top
      } else {
        document.execCommand("copy"); // run command to copy selected text to clipboard
      }
      // var coor = "Coordinates: (" + firstPointY + "," + lastPointY + ")";
      // document.getElementById("demo").innerHTML = coor + lastMouseEvent.buttons;
    }

    document.addEventListener("contextmenu", function (e) {
      if (mousePressedEventList.length > 3) {
        //因为这个事件触发的时间点并非一点在上面这个后面，所以这里的if条件不能和上面的合并；事件异步机制造成的吧
        e.preventDefault();
      }
    });

    mousePressedEventList = []; //放掉就重置
  }
}

document.body.addEventListener("mousemove", myFunction);