核心代码：
<！doctype html> <html xmlns = "http://www.w3.org/1999/xhtml"> <head> <meta http-equiv = "content-type" content = "text/html; charset = utf-8" " /> <title> </title> <style> #box {width：100px; height：100px; background：＃966; position：aspolute; left：100px; top：100px; cursor：pointer;} </head> <body> <body> <div id = "box"> div> </docurcimt; {width：math.max（document.documentelement.clientwidth、document.documentelement.scrollwidth）、height：math.max（document.documentelement.clientheight、document.documentelement.scrollheight.scrollheight）};} function comparenum（x、minnum、mannum） x <minnum：x = minnum; break;ケースx> maxnum：x = maxnum; break;デフォルト：x; } xを返します。 } box.style.left = '100px'box.style.top =' 100px'box.onmousedown = function（e）{var e = e || window.event; var maxl = getViewport（）。width-100、maxt = getViewport（）。height-100; this.startl = parseint（this.style.left）; this.startt = parseint（this.style.top）; //alert(e.clientx）this.startx = e.clientx; this.starty = e.clienty; // alert（maxl+'：'+maxt+'：'+l+'：'+t）doc.onmousemove = function（e）{posxy（e、0,0、maxl、maxt）; }; doc.onmouseup = function（）{doc.onmousemove = null; doc.onmouseup = null; }; false;} function posxy（e、minl、mint、maxl、maxt）{var e = e || window.event; var x = box.startl-（box.startx-e.clientx）; var y = box.startt-（box.starty-e.clienty）; box.style.left = comparenum（x、minl、maxl）+'px' box.style.top = comparenum（y、mint、maxt）+'px'} </script> </body> </html>[ctrl+a全选全选：如需引入外部js需刷新才能执行]