Detailed explanation of the steps to implement collision detection in JS-JS Tutorial-php.cn

Detailed explanation of the steps to implement collision detection in JS

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Release： 2018-05-23 10:05:56

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This time I will bring you a detailed explanation of the steps to implement collision detection with JS. What are the precautions for implementing collision detection with JS. The following is a practical case, let's take a look.

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title> JS碰撞检测</title>
<style>
p{width:100px;
  height:100px;
}
#box{background:red; position:absolute; }
#box1{background:green;position:absolute;top:300px; left:300px;}
</style>
<script>
//两个碰撞的盒子。是建立在一个不动的基础上。所以可以根据不动的盒子求出四个方向的left和top值。然后再判断其是否碰撞，且碰撞的过程随时改变其层级，（原需 var 8个变量，现在只需4个变量）
function collText(obj,left,top,obj1){
      var l1=obj.offsetLeft-obj.offsetWidth;
      var t1=obj.offsetTop-obj.offsetHeight;
      var r1=obj.offsetLeft+obj.offsetWidth;
      var b1=obj.offsetTop+obj.offsetHeight;
      if(left<l1||top<t1||left>r1||top>b1){
        obj.style.zIndex=3;
        obj1.style.zIndex=1;
        return true;
      }else{
        obj.style.zIndex=1;
        obj1.style.zIndex=3;
        return false;
      }
};
window.onload=function(){
  var oBox=document.getElementById('box');
  var oBox1=document.getElementById('box1');
  oBox.onmousedown=function(ev){
    var oEvent= ev  ||  event;
    var disX=oEvent.clientX-oBox.offsetLeft;
    var disY=oEvent.clientY-oBox.offsetTop;
    document.onmousemove=function(ev){
      var oEvent= ev ||  event;
      var l=oEvent.clientX-disX;
      var t=oEvent.clientY-disY;
      oBox.style.left=l+'px'  ;
      oBox.style.top=t+'px'  ;
      if(collText(oBox1,l,t,oBox)){
        oBox1.style.background='green';
      }else{
        oBox1.style.background='yellow';
      }
    };
    document.onmouseup=function(){
      document.onmousemove=null;
      document.onmouseup=null;
      oBox.reseaseCapture&&oBox.reseaseCapture();
    };
    oBox.setCapture&&oBox.setCapture();
    return false;
  }
  oBox1.onmousedown=function(ev){
    var oEvent= ev ||  event;
    var disX1=oEvent.clientX-oBox1.offsetLeft;
    var disY1=oEvent.clientY-oBox1.offsetTop;
    document.onmousemove=function(ev){
      var oEvent= ev ||  event;
      var le=oEvent.clientX-disX1;
      var to=oEvent.clientY-disY1;
      oBox1.style.left=le+'px'  ;
      oBox1.style.top=to+'px'  ;
      if(collText(oBox,le,to,oBox1)){
        oBox.style.background='red';
      }else{
        oBox.style.background='#000';
      }
    };
    document.onmouseup=function(){
      document.onmousemove=null;
      document.onmouseup=null;
      oBox1.reseaseCapture&&oBox1.reseaseCapture();
    }
    oBox1.setCapture&&oBox1.setCapture();
    return false;
  }
}
</script>
</head>
<body>
<p id="box"></p>
<p id="box1"></p>
</body>
</html>

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Here we useOnline HTML/CSS/JavaScriptRun toolhttp://tools.jb51.net/code/HtmlJsRun test run The effect is as follows (the color changes during collision determination):

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!