I am going to ask you a childish question about JavaScript. I asked you this question because I am beginner in JavaScript. I hope you will give me solution.
Code:
<!DOCTYPE html>
<html>
<body>

<p>Click the button to calculate x.</p>
<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction()
{
y=5;
z=2;
x=y+z;
document.getElementById("demo").innerHTML=x;
}
</script>

</body>
</html>
When I place the above code, it will show me following result:
Untitled.png

If I press button "try it" it will show me a result 7.

Now I want to know that how can I input different values of y and z and get value of x by using javascript code?

Please give me an example.