textarea 光标安插

<textarea id='target_area'onclick="setCaret(this);" onkeyup="setCaret(this);"></textarea>

//设置textarea光标位置
function setCaret(textObj){
		if(textObj.createTextRange){  
		   textObj.caretPos=document.selection.createRange().duplicate();  
		}
}
//光标位置插入内容
function insertAtCaret(textFeildValue){
	var textObj = document.getElementById('target_area');
	if(firefox){
		var start = textObj.selectionStart;
		var end = textObj.selectionEnd;
		textObj.value = textObj.value.substr(0,start) + textFeildValue + textObj.value.substr(end);
	}
    else
	{
		if(textObj.createTextRange && textObj.caretPos){     
			var caretPos=textObj.caretPos;    
			caretPos.text=caretPos.text.charAt(caretPos.text.length-1)==''?textFeildValue+'':textFeildValue;
		}else {
		  textObj.value+=textFeildValue;
		}
	}
}