web中拖拽函数的封装

<script>window.onload = function() {var oDiv = document.getElementById('div1');var oImg = document.getElementById('img1');drag(oImg);drag(oDiv);function drag(obj) {obj.onmousedown = function(ev) {var ev = ev || event;var disX = ev.clientX - this.offsetLeft;var disY = ev.clientY - this.offsetTop;if ( obj.setCapture ) {obj.setCapture();}document.onmousemove = function(ev) {var ev = ev || event;obj.style.left = ev.clientX - disX + 'px';obj.style.top = ev.clientY - disY + 'px';}document.onmouseup = function() {document.onmousemove = document.onmouseup = null;//释放全局捕获 releaseCapture();if ( obj.releaseCapture ) {obj.releaseCapture();}}return false;}}}</script>