js获得指定控件光标的坐标，兼容IE,Chrome,火狐等多种主流浏览器

直接上代码

var kingwolfofsky = {

    /**

    * 获取输入光标在页面中的坐标

    * @param  {HTMLElement} 输入框元素       

    * @return  {Object}  返回left和top,bottom

    */

    getInputPositon: function (elem) {

        if (document.selection) {   //IE Support

            elem.focus();

            var Sel = document.selection.createRange();

            return {

                left: Sel.boundingLeft,

                top: Sel.boundingTop,

                bottom: Sel.boundingTop + Sel.boundingHeight

            };

        } else {

            var that = this;

            var cloneDiv = '{$clone_div}', cloneLeft = '{$cloneLeft}', cloneFocus = '{$cloneFocus}', cloneRight = '{$cloneRight}';

            var none = '<span style="white-space:pre-wrap;"> </span>';

            var div = elem[cloneDiv] || document.createElement('div'), focus = elem[cloneFocus] || document.createElement('span');

            var text = elem[cloneLeft] || document.createElement('span');

            var offset = that._offset(elem), index = this._getFocus(elem), focusOffset = { left: 0, top: 0 };

            if (!elem[cloneDiv]) {

                elem[cloneDiv] = div, elem[cloneFocus] = focus;

                elem[cloneLeft] = text;

                div.appendChild(text);

                div.appendChild(focus);

                document.body.appendChild(div);

                focus.innerHTML = '|';

                focus.style.cssText = 'display:inline-block;width:0px;overflow:hidden;z-index:-100;word-wrap:break-word;word-break:break-all;';

                div.className = this._cloneStyle(elem);

                div.style.cssText = 'visibility:hidden;display:inline-block;position:absolute;z-index:-100;word-wrap:break-word;word-break:break-all;overflow:hidden;';

            };

            div.style.left = this._offset(elem).left + "px";

            div.style.top = this._offset(elem).top + "px";

            var strTmp = elem.value.substring(0, index).replace(/</g, '<').replace(/>/g, '>').replace(/\n/g, '<br/>').replace(/\s/g, none);

            text.innerHTML = strTmp;

            focus.style.display = 'inline-block';

            try { focusOffset = this._offset(focus); } catch (e) { };

            focus.style.display = 'none';

            return {

                left: focusOffset.left,

                top: focusOffset.top,

                bottom: focusOffset.bottom

            };

        }

    },

    // 克隆元素样式并返回类

    _cloneStyle: function (elem, cache) {

        if (!cache && elem['${cloneName}']) return elem['${cloneName}'];

        var className, name, rstyle = /^(number|string)$/;

        var rname = /^(content|outline|outlineWidth)$/; //Opera: content; IE8:outline && outlineWidth

        var cssText = [], sStyle = elem.style;

        for (name in sStyle) {

            if (!rname.test(name)) {

                val = this._getStyle(elem, name);

                if (val !== '' && rstyle.test(typeof val)) { // Firefox 4

                    name = name.replace(/([A-Z])/g, "-$1").toLowerCase();

                    cssText.push(name);

                    cssText.push(':');

                    cssText.push(val);

                    cssText.push(';');

                };

            };

        };

        cssText = cssText.join('');

        elem['${cloneName}'] = className = 'clone' + (new Date).getTime();

        this._addHeadStyle('.' + className + '{' + cssText + '}');

        return className;

    },

    // 向页头插入样式

    _addHeadStyle: function (content) {

        var style = this._style[document];

        if (!style) {

            style = this._style[document] = document.createElement('style');

            document.getElementsByTagName('head')[0].appendChild(style);

        };

        style.styleSheet && (style.styleSheet.cssText += content) || style.appendChild(document.createTextNode(content));

    },

    _style: {},

    // 获取最终样式

    _getStyle: 'getComputedStyle' in window ? function (elem, name) {

        return getComputedStyle(elem, null)[name];

    } : function (elem, name) {

        return elem.currentStyle[name];

    },

    // 获取光标在文本框的位置

    _getFocus: function (elem) {

        var index = 0;

        if (document.selection) {// IE Support

            elem.focus();

            var Sel = document.selection.createRange();

            if (elem.nodeName === 'TEXTAREA') {//textarea

                var Sel2 = Sel.duplicate();

                Sel2.moveToElementText(elem);

                var index = -1;

                while (Sel2.inRange(Sel)) {

                    Sel2.moveStart('character');

                    index++;

                };

            }

            else if (elem.nodeName === 'INPUT') {// input

                Sel.moveStart('character', -elem.value.length);

                index = Sel.text.length;

            }

        }

        else if (elem.selectionStart || elem.selectionStart == '0') { // Firefox support

            index = elem.selectionStart;

        }

        return (index);

    },

    // 获取元素在页面中位置

    _offset: function (elem) {

        var box = elem.getBoundingClientRect(), doc = elem.ownerDocument, body = doc.body, docElem = doc.documentElement;

        var clientTop = docElem.clientTop || body.clientTop || 0, clientLeft = docElem.clientLeft || body.clientLeft || 0;

        var top = box.top + (self.pageYOffset || docElem.scrollTop) - clientTop, left = box.left + (self.pageXOffset || docElem.scrollLeft) - clientLeft;

        return {

            left: left,

            top: top,

            right: left + box
4000
.width,

            bottom: top + box.height

        };

    }

};

function getPosition(ctrl) {

    var p = kingwolfofsky.getInputPositon(ctrl);

    document.getElementById('show').style.left = p.left + "px";

    document.getElementById('show').style.top = p.bottom + "px";

}

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调用代码：

 var elem = document.getElementById(控件ID);

 var p = kingwolfofsky.getInputPositon(elem);

p.left;//获得指定位置坐标

p.top;//同上

p.bottom;//同上