javascript 绘制矩形框
如果不考虑把整个代码封装起来， 大约5分钟里也可以写出类似的效果，为了把整个代码封装成一个对象，稍微借鉴了Pro Javascript Techniques书中的代例子的风格。Pro Javascript Techniques书中推荐的drag and drop 例子：http://boring.youngpup.net/2001/domdrag
Rect
var Rect = { //当前正在画的矩形对象 obj: null, //画布 container: null, //初始化函数 init: function(containerId){ Rect.container = document.getElementById(containerId); if(Rect.container){ //鼠标按下时开始画 Rect.container.onmousedown = Rect.start; } else{ alert('You should specify a valid container!'); } }, start: function(e){ var o = Rect.obj = document.createElement('div'); o.style.position = "absolute"; // mouseBeginX，mouseBeginY是辅助变量，记录下鼠标按下时的位置
o.style.left = o.mouseBeginX = Rect.getEvent(e).x; o.style.top = o.mouseBeginY = Rect.getEvent(e).y; o.style.height = 0; o.style.width = 0; o.style.border = "dotted black 1px"; //向o添加一个叉叉，点击叉叉可以删除这个矩形 var deleteLink = document.createElement('a'); deleteLink.href="#"; deleteLink.onclick = function(){ Rect.container.removeChild(this.parentNode); //this.parentNode.style.display = "none"; //alert(this.tagName); } deleteLink.innerText = "x";
o.appendChild(deleteLink); //把当前画出的对象加入到画布中 Rect.container.appendChild(o); //处理onmousemove事件 Rect.container.onmousemove = Rect.move; //处理onmouseup事件 Rect.container.onmouseup = Rect.end; }, move: function(e){ var o = Rect.obj; //dx，dy是鼠标移动的距离 var dx = Rect.getEvent(e).x - o.mouseBeginX; var dy = Rect.getEvent(e).y - o.mouseBeginY; //如果dx，dy
增加一个按钮，可以关闭绘画效果，用来配合测试删除功能
//测试代码开始 //初始化 Rect.init("main");
document.getElementById('t').onclick = function(){ Rect.container.onmousedown = null; };
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]