Question

This is my javascript code:

var num1;
function press_Button(){
    num1 = 3;           
}

Then I have a button with this: onclick="press_Button()"

and in the HTML is this:

<script type="text/javascript">
    document.write(num1);
</script>

The page displays the variable as undefined, even after hitting the button, and I can’t figure out why.

Help!

Answer 1

You’ll need to update the display of num1 after you call press_Button. What I would do is ditch the document.write, and instead make a span:

<span id="num1Display"></span>

And then:

function press_Button() {
    num1 = 3;           
    document.getElementById("num1Display").textContent = num1;
}

Or, if you need this to work on ancient browsers that don’t like textContent, you could do:

function press_Button() {
    num1 = 3;           
    document.getElementById("num1Display").innerHTML = num1;
}