uselessCounter.js

let num = 0 //declare a variable whose initial value is zero

//function declaration
function increaseNum(){
    num++ //increase the value of num by 1  using the increment operator   

    //get the reference to the body element
    let bodyElement = document.getElementsByTagName('body')[0]

    //... and set its text value to the value of num
    bodyElement.innerText = num
}

//run my increaseNum function at most every 1000 milliseconds (could be later)
window.setInterval(increaseNum, 1000)