テキストボックスのHTML実装は、内容だけを読み取って変更することはできない

 <! -- method 1: onfocus=this.blur() leaves focus when mouse is not placed -->
<input type="text" name="input1" value="China" onfocus=this.blur()> 
<! -- Method 2:readonly The text does not change color and is not editable -- >
<input type="text" name="input1" value="China" readonly> 
<input type="text" name="input1" value="China" readonly="true"> 
<! -- Method 3: disabled The text will be grayed out and not editable. -->
<input type="text" name="input1" value="China" disabled="true">