chikoski · December 25, 2015 01:49
diff --git a/jsbin.atOSaNo.css b/jsbin.atOSaNo.css
 .error{
  font-weight: bold;
  color: rgb(240, 240, 240);
  background-color: rgb(240, 48, 48);
  padding: 10px;
 }
diff --git a/jsbin.atOSaNo.html b/jsbin.atOSaNo.html
 <!DOCTYPE html>
 <html>
 <head>
 <meta charset=utf-8 />
 <title>押すなよ！</title>
 </head>
 <body>
  <button id="pressme" type="button"押すなよ！</button>
  <div id="message">
    ここの色が変わります。
  </div>
 </body>
 </html>
diff --git a/jsbin.atOSaNo.js b/jsbin.atOSaNo.js
 var buttonPressed = function(event){  
  var div = document.getElementById("message");
  div.setAttribute("class", "error");
 };
 
 var btn = document.getElementById("pressme");
 btn.onclick = buttonPressed;
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset=utf-8 />
	<title>押すなよ！</title>
	</head>
	<body>
	<button id="pressme" type="button"押すなよ！</button>
	<div id="message">
	ここの色が変わります。
	</div>
	</body>
	</html>
	var buttonPressed = function(event){
	var div = document.getElementById("message");
	div.setAttribute("class", "error");
	};

	var btn = document.getElementById("pressme");
	btn.onclick = buttonPressed;