JavaScript拖拽图片四
现在用Firefox最新版本13.0测试，不work，图片会自动回到原位。
安装firebug扩展后调试一下。
到console窗口点击enable后，
错误信息是：
window.event is undefined.
Firefox不支持window.event，因此所有用到event的地方要类似这样写：
/*global window */function getEvent(e) {'use strict';return e || window.event;}function getTarget(e) {'use strict';return e.currentTarget || e.srcElement;}function getPos(e) {'use strict';return {x: e.x || e.clientX,y: e.y || e.clientY};}function mouseDown(e) {'use strict';e = getEvent(e);window.dragObj = getTarget(e);if (e.preventDefault) {e.preventDefault();} else {e.returnValue = false;}if (window.dragObj !== null) {var pos = getPos(e);window.clickLeft = pos.x - parseInt(window.dragObj.style.left, 10);window.clickTop = pos.y - parseInt(window.dragObj.style.top, 10);window.dragObj.style.zIndex += 1;}}/** * IE6.0 need this */function mouseStop(e) {'use strict';e = getEvent(e);e.returnValue = false;}function mouseMove(e) {'use strict';e = getEvent(e);if (window.dragObj !== null) {var pos = getPos(e);window.dragObj.style.left = pos.x - window.clickLeft;window.dragObj.style.top = pos.y - window.clickTop;}}function mouseUp() {'use strict';window.dragObj = null;}function init() {'use strict';window.dragObj = null;window.document.onmousemove = mouseMove;window.document.onmouseup = mouseUp;window.document.ondragstart = mouseStop;}