http://blog.csdn.net/kingwolfofsky/article/details/6586029
index.html
<!DOCTYPE html> <html> <head> <title>InputPostion</title> <script type="text/javascript" src="kingwolfofsky.js""></script> <script type="text/javascript"> function show(elem) { var p = kingwolfofsky.getInputPositon(elem); var s = document.getElementById('show'); s.style.top = p.bottom+'px'; s.style.left = p.left + 'px'; s.style.display = 'inherit'; } </script> </head> <body> <textarea id="text" onkeyup="show(this)" style=" 340px; height: 210px;"></textarea> <br /> <input type="text" onkeyup="show(this)" style=" 340px;" /> <div id="show" style=" 34px; height: 13px; background: #eee; position: absolute;border:1px solid grey;font-size:13px; display:none;">Tips</div> </body> </html>
kingwolfofsky.js
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;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(/ /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.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"; }