学习drag and drop js实现代码经典之作_javascript技巧

Pro Javascript Techniques书中推荐的drag and drop 例子：http://boring.youngpup.net/2001/domdrag

<title>Drag</title> <style type="text/css"> </style> <script type="text/javascript"> var Drag = { //当前被drag的对象 obj: null, //初始化 init: function(id){ var o = document.getElementById(id); //当onmousedown开始拖拽 o.onmousedown = Drag.start; }, start: function(e){ var o = Drag.obj = this; //lastMouseX，lastMouseY记录上次鼠标的位置 o.lastMouseX = Drag.getEvent(e).x; o.lastMouseY = Drag.getEvent(e).y; //当onmousemove开始移动 document.onmousemove = Drag.move; //当onmouseup终止拖拽 document.onmouseup = Drag.end; }, move: function(e){ var o = Drag.obj; //dx, dy表示鼠标移动的距离 var dx = Drag.getEvent(e).x - o.lastMouseX; var dy = Drag.getEvent(e).y - o.lastMouseY; //因为element.style.left通常返回的结果是'200px'的形式，所以要用parseInt转化 var left = parseInt(o.style.left) + dx ; var top = parseInt(o.style.top) + dy; o.style.left = left; o.style.top = top; o.lastMouseX = Drag.getEvent(e).x; o.lastMouseY = Drag.getEvent(e).y; }, end: function(e){ document.onmousemove = null; document.onMouseup = null; Drag.obj = null; }, //辅助函数，处理IE和FF不同的event模型 getEvent: function(e){ if (typeof e == 'undefined'){ e = window.event; } //alert(e.x?e.x : e.layerX); if(typeof e.x == 'undefined'){ e.x = e.layerX;//复制了n遍，到了csdn就变成ee.x了 } if(typeof e.y == 'undefined'){ e.y = e.layerY;//复制了n遍，到了csdn就变成ee.x了 } return e; } }; </script> <div id="r" style="position:absolute; left:100px; top:100px; background-color:red; height:80px; width:80px;"></div> <div id="g" style="position:absolute; left:250px; top:100px; background-color:green; height:80px; width:80px;"></div> <div id="b" style="position:absolute; left:400px; top:100px; background-color:blue; height:80px; width:80px;"></div> <script type="text/javascript"> //测试代码开始，使三个div具有drag and drop的能力。 Drag.init('r'); Drag.init('g'); Drag.init('b'); </script>
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