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Detailed explanation of the steps to implement collision detection in JS

php中世界最好的语言Original: 2018-05-23 10:05:562181browse

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>

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!

Detailed explanation of the steps to implement collision detection in JS

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