HTML/Javascript Button Click Counter

Question 1

Use var instead of int for your clicks variable generation and onClick instead of click as your function name:

var clicks = 0;

function onClick() {
  clicks += 1;
  document.getElementById("clicks").innerHTML = clicks;
};

<button type="button" onClick="onClick()">Click me</button>
<p>Clicks: <a id="clicks">0</a></p>

In JavaScript variables are declared with the var keyword. There are no tags like int, bool, string... to declare variables. You can get the type of a variable with 'typeof(yourvariable)', more support about this you find on Google.

And the name 'click' is reserved by JavaScript for function names so you have to use something else.

Question 2

Don't use the word "click" as the function name. It's a reserved keyword in JavaScript. In the bellow code I’ve used "hello" function instead of "click"

<html>
<head>
    <title>Space Clicker</title>
</head>

<body>
    <script type="text/javascript">

    var clicks = 0;
    function hello() {
        clicks += 1;
        document.getElementById("clicks").innerHTML = clicks;
    };
    </script>
    <button type="button" onclick="hello()">Click me</button>
    <p>Clicks: <a id="clicks">0</a></p>

</body></html>

Question 3

After looking at the code you're having typos, here is the updated code

var clicks = 0; // should be var not int
    function clickME() {
        clicks += 1;
        document.getElementById("clicks").innerHTML = clicks; //getElementById() not getElementByID() Which you corrected in edit
 }

Demo

Note: Don't use in-built handlers, as .click() is javascript function try giving different name like clickME()

Question 4

Through this code, you can get click count on a button.

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>Button</title>
    <link rel="stylesheet" type="text/css" href="css/button.css">
</head>
<body>
    <script src="js/button.js" type="text/javascript"></script>

    <button id="btn" class="btnst" onclick="myFunction()">0</button>
</body>
</html>
 ----------JAVASCRIPT----------
let count = 0;
function myFunction() {
  count+=1;
  document.getElementById("btn").innerHTML = count;

 }

Question 5

    <!DOCTYPE html>
<html>
<head>
<script>
     var clicks = 0;
    function myFunction() {

        clicks += 1;
        document.getElementById("demo").innerHTML = clicks;


    }
</script>
</head>
<body>

<p>Click the button to trigger a function.</p>

<button onclick="myFunction()">Click me</button>

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

</body>
</html>

This should work for you :) Yes var should be used