show a form when a button in s click javascript code example

Example 1: how to call a function with a button in javascript

<script>
		function myFunction()
		{
			document.write("<h1>HELLO</h1>")
		}
	</script>
<button onclick="myFunction()">Click</button>

Example 2: javascript onclick

// The element id (TheElementID) and var name (myElement) can be named anything.
var myElement = document.getElementByID('TheElementID');
myElement.onclick = function() {
	// Carry out a function here...
}