How to use the keyboard to control div movement in js-JS Tutorial-php.cn

How to use the keyboard to control div movement in js

王林

Release： 2020-04-29 09:10:56

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How to use the keyboard to control div movement in js

Description:

div realizes the movement of div blocks up, down, left and right through keyboard events

Effect:

How to use the keyboard to control div movement in js

(Video tutorial recommendation: js video tutorial)

js code:

var Method=(function () {
  return {
    EVENT_ID:"event_id",
    loadImage:function (arr) {
      var img=new Image();
      img.arr=arr;
      img.list=[];
      img.num=0;
//      如果DOM对象下的事件侦听没有被删除掉，将会常驻堆中
//      一旦触发了这个事件需要的条件，就会继续执行事件函数
      img.addEventListener("load",this.loadHandler);
      img.self=this;
      img.src=arr[img.num];
    },
    loadHandler:function (e) {
      this.list.push(this.cloneNode(false));
      this.num++;
      if(this.num>this.arr.length-1){
        this.removeEventListener("load",this.self.loadHandler);
        var evt=new Event(Method.EVENT_ID);
        evt.list=this.list;
        document.dispatchEvent(evt);
        return;
      }
      this.src=this.arr[this.num];
    },
    $c:function (type,parent,style) {
      var elem=document.createElement(type);
      if(parent) parent.appendChild(elem);
      for(var key in style){
        elem.style[key]=style[key];
      }
      return elem;
    },
    divColor: function () {
      var col="#";//这个字符串第一位为# 颜色的格式
      for(var i=0;i<6;i++){
        col+=parseInt(Math.random()*16).toString(16);//rondom*16后的随机值即为0-1*16==0-16;  toString(16)为转化为16进制
      }
      return col;//最后返回一个七位的值 格式即为#nnnnnn 颜色的格式
    },
    random:function (min,max) {
      max=Math.max(min,max);
      min=Math.min(min,max);
      return Math.floor(Math.random()*(max-min)+min);
    },
    dragElem:function (elem) {
      elem.addEventListener("mousedown",this.mouseDragHandler);
      elem.self=this;
    },
    removeDrag:function (elem) {
      elem.removeEventListener("mousedown",this.mouseDragHandler);
    },
    mouseDragHandler:function (e) {
      if(e.type==="mousedown"){
        e.stopPropagation();
        e.preventDefault();
        document.point={x:e.offsetX,y:e.offsetY};
        document.elem=this;
        this.addEventListener("mouseup",this.self.mouseDragHandler);
        document.addEventListener("mousemove",this.self.mouseDragHandler);
      }else if(e.type==="mousemove"){
        this.elem.style.left=e.x-this.point.x+"px";
        this.elem.style.top=e.y-this.point.y+"px";
      }else if(e.type==="mouseup"){
        this.removeEventListener("mouseup",this.self.mouseDragHandler);
        document.removeEventListener("mousemove",this.self.mouseDragHandler);
      }
    }
  }
})();

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html code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <script src="js/Method.js"></script>
</head>
<body>
<script>
  var div;
  var code=[];
  var speed=2;
  var bool=false;
  init();
  function init() {
    div=Method.$c("div",document.body,{
      width:"50px",
      height:"50px",
      backgroundColor:"red",
      position:"absolute",
      left:0,
      top:0
    });
    window.addEventListener("keydown",keyHandler);
    window.addEventListener("keyup",keyHandler);
    setInterval(animation,16);
  }
 
  function keyHandler(e) {
    if(e.type==="keydown" && (!bool || code.indexOf(e.keyCode)===-1)){
      bool=true;
      code.push(e.keyCode);
    }else if(e.type==="keyup"){
      bool=false;
      code.length=0;
    }
  }
 
  function animation() {
    if(!bool)return;
    for(var i=0;i<code.length;i++){
      switch (code[i]){
        case 37:
          div.style.left=div.offsetLeft-speed+"px";
          break;
        case 38:
          div.style.top=div.offsetTop-speed+"px";
          break;
        case 39:
          div.style.left=div.offsetLeft+speed+"px";
          break;
        case 40:
          div.style.top=div.offsetTop+speed+"px";
          break;
      }
    }
  }
</script>
</body>
</html>

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