1.背景：实现在textarea光标位置插入文字并移动光标到文字末尾
如果每次通过val("ss")赋值的形式插入文字到textarea中，会将上一次赋的值覆盖掉。
2.思路：
<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Sliding Menu Effect</title>
<script type="text/javascript" language="javascript" src="jquery-2.1.1.min.js"></script>
<script type="text/javascript">
function insertText(obj,str) {
if (document.selection) {
var sel = document.selection.createRange();
sel.text = str;
} else if (typeof obj.selectionStart === 'number' && typeof obj.selectionEnd === 'number') {
var startPos = obj.selectionStart,
endPos = obj.selectionEnd,
cursorPos = startPos,
tmpStr = obj.value;
obj.value = tmpStr.substring(0, startPos) + str + tmpStr.substring(endPos, tmpStr.length);
cursorPos += str.length;
obj.selectionStart = obj.selectionEnd = cursorPos;
} else {
obj.value += str;
}
}
function moveEnd(obj){
obj.focus();
var len = obj.value.length;
if (document.selection) {
var sel = obj.createTextRange();
sel.moveStart('character',len);
sel.collapse();
sel.select();
} else if (typeof obj.selectionStart == 'number' && typeof obj.selectionEnd == 'number') {
obj.selectionStart = obj.selectionEnd = len;
}
}
</script>
</head>
<body>
<input type="button" onclick="insertText(document.getElementById('text'),' 插入字符啊啊啊啊')" value="插入文字"></input>
<input type="button" onclick="moveEnd(document.getElementById('text'))" value="光标移到末尾"></input>
<textarea name="" id="text" cols="30" rows="10"></textarea>
</body>
</html>