functions.html

<html>
<head>
<title>Javascript Functions Example</title>
</head>
<body>

<h1>Javascript Functions</h1>

<script type="text/javascript">

function chooseColour() {
    var colour = prompt("What is your favourite colour?");
    if (colour != "") {
        document.body.style.backgroundColor = colour;
    }
}

</script>

<a href="javascript: chooseColour();">Choose Colour</a>

</body>
</html>