<body>
<div id="div1"></div>
</body>
<style> #div1 {width: 100px; height: 100px; background: red; position: absolute; left: 500px; top: 200px;} </style>
<script> window.onload = function() { var oDiv = document.getElementById(‘div1‘); oDiv.onmousedown = function(ev) { var ev = ev || event; var disW = this.offsetWidth; var disX = ev.clientX; var disL = this.offsetLeft; var b = ‘‘; if ( disX > disL + disW - 10 ) { //alert( ‘right‘ ); b = ‘right‘; } if ( disX < disL + 10 ) { //alert( ‘left‘ ); b = ‘left‘; } document.onmousemove = function(ev) { var ev = ev || event; switch( b ) { case ‘left‘: oDiv.style.width = disW - ( ev.clientX - disX ) + ‘px‘; oDiv.style.left = disL + ( ev.clientX - disX ) + ‘px‘; break; case ‘right‘: oDiv.style.width = disW + ( ev.clientX - disX ) + ‘px‘; break; } } document.onmouseup = function() { document.onmousemove = document.onmouseup = null; } return false; } } </script>
原文：http://www.cnblogs.com/chiangyibo/p/6680460.html