TLDR; Everyone lied to you when they said let and const don't create global variables. They absolutely do .. it's just that they don't create window. global variables. More on reddit.com

The number one thing I've seen writing performant JavaScript code has been making sure that things stay as unboxed primitives (ints, double, etc). Preferably in large typed arrays. Chances are your function itself isn't that hot, I bet the loop is though. Declare primitives once at the top of the function an they'll get allocated on the stack and incur zero GC. (Unless you do something like myInt["someProp"] = "something", in which case it's boxed and slow) More on reddit.com

http://forums.rpgmakerweb.com/index.php?/topic/46456-rpg-maker-mv-script-call-list/ More on reddit.com

Stick with the class. You're going to be more comfortable there and don't worry about anyone saying you shouldn't use OOP. class Rectangle { constructor (x, y, width, height) { this.x = x; // instance variables this.y = y; this.width = width; this.height = height; this.whatever = true; } get area () { // instance property return this.width * this.height; } rotate () { // instance method [this.width, this.height] = [this.height, this.width]; } static fromElement(element) { // class method const bounds = element.getBoundingClientRect(); return new Rectangle(bounds.left, bounds.top, bounds.width, bounds.height); } } const rect = new Rectangle(0,0,200,300); console.log(rect.width); // 200 console.log(rect.area); // 60000 rect.rotate(); console.log(rect.width); // 300 const rect2 = Rectangle.fromElement(document.getElementById('foo')); In the larger scheme of things, the class syntax is still pretty new, so you won't see it being used everywhere, but it should be considered the preferred syntax moving forward for class/constructor definitions in JavaScript. Generally speaking, if you see references to prototype you're looking at legacy code from before class was available. More on reddit.com