/// bad
onclick="double_increment()"

/// good
const button = document.getElementById("some_id");
button.addEventListener("click", double_increment);

function Incrementer(name, value) {
   /// bad
   let mydiv = document.getElementById('mydiv');
}

class Incrementer {
   /// still bad though
   static target = "mydiv"
}

/// bad
that.increment = function() {
        var i = parseInt(that.span.textContent) + 1;
        that.span.innerHTML = i;
}

/// better
that.i = value;

//increments value
that.increment = function() {
        that.i++;
}

//updates UI
that.update = function(){
        that.span.innerHTML = that.i;
}

// Method that should be called on button click
that.handleOnClick = function(){
   that.increment();
   that.update();
}

/// bad
function double_increment() {
    incrementer1.increment();
    incrementer2.increment();
}