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JavaScript使用面向对象实现的拖拽功能详解

程序员文章站 2023-12-01 21:33:58
本文实例讲述了javascript使用面向对象实现的拖拽功能。分享给大家供大家参考，具体如下： 面向对象有个前提： 前提：所有东西都必须包含在onload里...

本文实例讲述了javascript使用面向对象实现的拖拽功能。分享给大家供大家参考，具体如下：

面向对象有个前提：

  • 前提：所有东西都必须包含在onload里
  • 改写：不能有函数嵌套，可以有全局变量
  • 过程，如下
    • onload改成构造函数，
    • 全局变量改成属性（通过this）
    • 函数改写成方法
<!doctype html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>面向对象的继承-1</title>
<style>
#div1 {width: 100px; height: 100px; background: red; position: absolute;}
</style>
<script>
window.onload = function() {
  var odiv = document.getelementbyid('div1');
  odiv.onmousedown = function(ev) {
    var ev = ev || event;
    var disx = ev.clientx - this.offsetleft;
    var disy = ev.clienty - this.offsettop;
    document.onmousemove = function(ev) {
      var ev = ev || event;
      odiv.style.left = ev.clientx - disx + 'px';
      odiv.style.top = ev.clienty - disy + 'px';
    }
    document.onmouseup = function() {
      document.onmousemove = document.onmouseup = null;
    }
  }
}
</script>
</head>
<body>
  <div id="div1"></div>
</body>
</html>

把局部变量改成全局变量

<!doctype html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>面向对象的继承-2</title>
<style>
#div1 {width: 100px; height: 100px; background: red; position: absolute;}
</style>
<script>
var odiv=null;
var disx=0;
var disy=0;
window.onload = function() {
  odiv = document.getelementbyid('div1');
  odiv.onmousedown = fndown;
}
function fnmove(ev) {
  var ev = ev || event;
  odiv.style.left = ev.clientx - disx + 'px';
  odiv.style.top = ev.clienty - disy + 'px';
}
function fnup() {
  document.onmousemove = document.onmouseup = null;
}
function fndown(ev) {
  var ev = ev || event;
  disx = ev.clientx - this.offsetleft;
  disy = ev.clienty - this.offsettop;
  document.onmousemove = fnmove;
  document.onmouseup =fnup;
}
</script>
</head>
<body>
  <div id="div1"></div>
</body>
</html>

引用块内容

<!doctype html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>面向对象的继承-2</title>
<style>
#div1 {width: 100px; height: 100px; background: red; position: absolute;}
#div2 {width: 100px; height: 100px; background: red; position: absolute;top:120px;}
</style>
<script>
window.onload=function(){
  new drag('div1');
  new drag('div2');
}
function drag(id) {
  var _this=this;
  this.disx=0;
  this.disy=0;
  this.odiv = document.getelementbyid(id);
  this.odiv.onmousedown = function(){
    _this.fndown()
  };
}
drag.prototype.fndown=function (ev) {
  var ev = ev || event;
  var _this=this;
  this.disx = ev.clientx - this.odiv.offsetleft;
  this.disy = ev.clienty - this.odiv.offsettop;
  document.onmousemove = function(){
    _this.fnmove();
  };
  document.onmouseup =function(){
    _this.fnup();
  };
}
drag.prototype.fnmove=function(ev) {
  var ev = ev || event;
  this.odiv.style.left = ev.clientx - this.disx + 'px';
  this.odiv.style.top = ev.clienty - this.disy + 'px';
}
drag.prototype.fnup=function () {
  document.onmousemove = null;
  document.onmouseup = null
}
</script>
</head>
<body>
  <div id="div1"></div>
  <div id="div2"></div>
</body>
</html>


<!doctype html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>面向对象的继承-2</title>
<style>
#div1 {width: 100px; height: 100px; background: red; position: absolute;}
#div2 {width: 100px; height: 100px; background: red; position: absolute;top:120px;}
</style>
<script>
window.onload=function(){
  new drag('div1');
  new drag('div2');
}
function drag(id) {
  var _this=this;
  this.disx=0;
  this.disy=0;
  this.odiv = document.getelementbyid(id);
  this.odiv.onmousedown = function(){
    _this.fndown()
  };
}
drag.prototype.fndown=function (ev) {
  var ev = ev || event;
  var _this=this;
  this.disx = ev.clientx - this.odiv.offsetleft;
  this.disy = ev.clienty - this.odiv.offsettop;
  document.onmousemove = function(){
    _this.fnmove();
  };
  document.onmouseup =function(){
    _this.fnup();
  };
}
drag.prototype.fnmove=function(ev) {
  var ev = ev || event;
  this.odiv.style.left = ev.clientx - this.disx + 'px';
  this.odiv.style.top = ev.clienty - this.disy + 'px';
}
drag.prototype.fnup=function () {
  document.onmousemove = null;
  document.onmouseup = null
}
</script>
</head>
<body>
  <div id="div1"></div>
  <div id="div2"></div>
</body>
</html>

感兴趣的朋友可以使用在线html/css/javascript代码运行工具：http://tools.jb51.net/code/htmljsrun测试一下运行效果。

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希望本文所述对大家javascript程序设计有所帮助。

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