jonahb/prime.html

## prime.html
<html>
  <head>
    <meta charset="utf-8">
    <title>Is n prime?</title>
    <style>
      body {
        margin-top: 250px;
        font-family: 'San Francisco', Helvetica, sans-serif;
        font-size: 64px;
        text-align: center;
      }

      a {
        font-size: 32px;
      }

      a:hover {
        cursor: pointer;
      }

      #yes:hover {
        color: blue;
      }

      #no:hover {
        color: red;
      }

      #n {
        font-weight: bold;
      }

      #factors {
        margin-top: 48px;
        font-size: 16px;
        color: #999;
      }
    </style>
  </head>
  <body onload="next();">
    <script>
      var n;

      function next() {
        n = 100 + Math.ceil(Math.random() * 9900)
        document.getElementById("n").textContent = n.toString();
      }

      function answer(answer) {
        var factors = factorize(n);
        var isPrime = (factors.length === 0);

        alert((answer === isPrime) ? "RIGHT!" : "WRONG :(");

        document.getElementById("factors").textContent = isPrime ?
          n.toString() + " is prime" :
          "Factors of " + n + " — " + factors.join(", ");

        next();
      }

      function factorize(n) {
        var factors = [];
        var k;

        for (k = 2; k <= Math.sqrt(n); ++k) {
          if (n % k === 0) {
            factors.push(k);
            factors.push(n / k)
          }
        }

        return factors.sort(function(a, b) { return a - b; });
      }
    </script>

    Is <span id="n"></span> prime?<br>
    <a id="yes" onclick="answer(true);">Yes</a>
    <a id="no" onclick="answer(false);">No</a><br>
    <div id="factors"></div>
  </body>
</html>
	<html>
	<head>
	<meta charset="utf-8">
	<title>Is n prime?</title>
	<style>
	body {
	margin-top: 250px;
	font-family: 'San Francisco', Helvetica, sans-serif;
	font-size: 64px;
	text-align: center;
	}

	a {
	font-size: 32px;
	}

	a:hover {
	cursor: pointer;
	}

	#yes:hover {
	color: blue;
	}

	#no:hover {
	color: red;
	}

	#n {
	font-weight: bold;
	}

	#factors {
	margin-top: 48px;
	font-size: 16px;
	color: #999;
	}
	</style>
	</head>
	<body onload="next();">
	<script>
	var n;

	function next() {
	n = 100 + Math.ceil(Math.random() * 9900)
	document.getElementById("n").textContent = n.toString();
	}

	function answer(answer) {
	var factors = factorize(n);
	var isPrime = (factors.length === 0);

	alert((answer === isPrime) ? "RIGHT!" : "WRONG :(");

	document.getElementById("factors").textContent = isPrime ?
	n.toString() + " is prime" :
	"Factors of " + n + " — " + factors.join(", ");

	next();
	}

	function factorize(n) {
	var factors = [];
	var k;

	for (k = 2; k <= Math.sqrt(n); ++k) {
	if (n % k === 0) {
	factors.push(k);
	factors.push(n / k)
	}
	}

	return factors.sort(function(a, b) { return a - b; });
	}
	</script>

	Is <span id="n"></span> prime?<br>
	<a id="yes" onclick="answer(true);">Yes</a>
	<a id="no" onclick="answer(false);">No</a><br>
	<div id="factors"></div>
	</body>
	</html>