为什么JavaScript中的Underline功能不起作用？

Question

 function underline() { var text = document.getElementById("note_header").style.textDecoration; if (text == 'normal') { document.getElementById("note_header").style.textDecoration = 'Underline'; } else { document.getElementById("note_header").style.textDecoration = 'normal'; } } 

 <input id="btn" type="button" value="Underline" name="btn" onclick="underline()"> 

Answer 1

normal is not an accepted value for text-decoration . Use none instead.

 function underline(){ var text = document.getElementById("note_header").style.textDecoration; if (text !== 'underline'){ document.getElementById("note_header").style.textDecoration = 'underline'; } else{ document.getElementById("note_header").style.textDecoration = 'none'; } } 

 <textarea id="note_header" rows="3" cols="15"> That's my note </textarea><br/> <input id="btn" type="button" value="Underline" name="btn" onclick="underline()"> 

Answer 2

Try this

 function underline(){ var text = document.getElementById("note_header").style.textDecoration; if (text == 'none'){ document.getElementById("note_header").style.textDecoration = 'Underline'; } else{ document.getElementById("note_header").style.textDecoration = 'none'; } } 

 <a href="#" id="note_header" style="text-decoration:none;">This is anchor</a> <input id="btn" type="button" value="Underline" name="btn" onclick="underline()">