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></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></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></div> <div></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></div> <div></div> </body> </html>
感兴趣的朋友可以使用在线HTML/CSS/JavaScript代码运行工具：测试一下运行效果。