<div contenteditable=true id="divTest"></div>

var cursor = 0; // 光标位置  

document.onselectionchange = function () {

var range = document.selection.createRange();

var srcele = range.parentElement();//获取到当前元素

var copy = document.body.createTextRange();

copy.moveToElementText(srcele);

for (cursor = 0; copy.compareEndPoints("StartToStart", range) < 0; cursor++) {

 copy.moveStart("character", 1);//改变光标位置，实际上我们是在记录cursor的数量.

}

}

function moveEnd(obj) {

lyTXT1.focus();

var r = document.selection.createRange();

//因为这里死从当前光标开始移动的(好像文本框的是从0算起.)所以我们需要拿到当前光标位置，然后就可以计算出要移动多少位了，这样就可以把光标移动到想要的位置了

r.moveStart('character', lyTXT1.innerText.length - cursor);

r.collapse(true);

r.select();

}

function moveEnd(obj) {

lyTXT1.focus();

var r = document.selection.createRange();

//因为这里死从当前光标开始移动的(好像文本框的是从0算起.)所以我们需要拿到当前光标位置，然后就可以计算出要移动多少位了，这样就可以把光标移动到想要的位置了

r.moveStart('character', lyTXT1.innerText.length - cursor);

r.collapse(true);

r.select();

}

<button type="button" onclick="document.getElementById('test').focus(); insertHtmlAtCaret('<b>INSERTED</b>');">插入字符</button>

<div contentEditable="true" style="height:50px; border:2px solid red;" id="test"> </div>

function insertHtmlAtCaret(html) {

var sel, range;

if (window.getSelection) {

// IE9 and non-IE

sel = window.getSelection();

if (sel.getRangeAt && sel.rangeCount) {

range = sel.getRangeAt(0);

range.deleteContents();

// Range.createContextualFragment() would be useful here but is

// non-standard and not supported in all browsers (IE9, for one)

var el = document.createElement("div");

el.innerHTML = html;

var frag = document.createDocumentFragment(), node, lastNode;

while ( (node = el.firstChild) ) {

lastNode = frag.appendChild(node);

}

range.insertNode(frag);

// Preserve the selection

if (lastNode) {

range = range.cloneRange();

range.setStartAfter(lastNode);

range.collapse(true);

sel.removeAllRanges();

sel.addRange(range);

}

}

} else if (document.selection && document.selection.type != "Control") {

// IE < 9

document.selection.createRange().pasteHTML(html);

}

}