一个关于TextArea方面的技巧问题（高分求教）

Question

<textarea rows="3" cols="40" id="txt1">123456</textarea>
<input type="button" value="+" onclick="txt1.focus();document.selection.createRange().text='+';">
<input type="button" value="-" onclick="txt1.focus();document.selection.createRange().text='-';">
<input type="button" value="*" onclick="txt1.focus();document.selection.createRange().text='*';">
<input type="button" value="/" onclick="txt1.focus();document.selection.createRange().text='/';">

Answer 1

<textarea rows="3" cols="40" id="txt1">123456</textarea><input type="button" value="+" onclick="txt1.focus();document.execCommand('paste',false,'+');">
<input type="button" value="-" onclick="txt1.focus();document.execCommand('paste',false,'-');">
<input type="button" value="*" onclick="txt1.focus();document.execCommand('paste',false,'*');">
<input type="button" value="/" onclick="txt1.focus();document.execCommand('paste',false,'/');;"> 

Answer 2

<textarea rows="3" cols="40" id="txt1">123456</textarea>
<input type="button" value="+" onclick="javascript:txt1.value+='+';">