How to increment a variable after button press

Question

I was wondering how I could increase a variable when a button is clicked. here is my code. Can somebody point me in the right direction? thanks.

I am thinking when the button1 is clicked it will increase team 1's score by like 10, and will decrease if it is clicked again if that is necessary.

var Team2;
var Team2 == 0;
var Team1;
var Team1 == 0;
document.getElementById("calc").innerHTML = Team1;



function clicked(button1)
{
var team1 = team1 + 45
}
</SCRIPT>
<p>
Players for Team 1

Answer 1

First, the variable part: suppose you define a variable var value = 0. To increase it by 10, you can write value = value + 10, but in JavaScript this can be shorten to:

value += 10

The same way, to decrease it, just write value -= 10.

To call the function, you write onClick="someFunction()" (not the best practice), and then you define the function:

function someFunction(){
  value += 10
};

This is the working fiddle: https://jsfiddle.net/gerardofurtado/6qh1yhsj/

If you want to see how to do the same thing without the onClick="someFunction()" part, here is a fiddle: https://jsfiddle.net/gerardofurtado/wff8mph3/

PS: I see that in your code you wrote var team2 == 0. In JavaScript, two equal signs make a comparison operator: http://www.w3schools.com/js/js_comparisons.asp

PS2: In JavaScript, you have to mind the scope. Once you defined the var team1, you can change it inside the function just by writing team1. But if you do as you did:

function someFunction(){
  var team1 = team1 + 45
};

This team1 is not the same previous variable team1 defined outside the function. It's a different variable. And, as the team1 to the right of the equal sign is not defined, this will return a NaN (Not-A-Number).