Private fields in Javascript

I’ve always learned that Javascript didn’t support private fields. You could use closures as a ‘language hack’ to keep information private but it is not at the same level of simplicity:

	var Animal = (function () {
	var name;
	function Animal(theName) {
	name = theName;
	}
	return Animal;
	}());

view raw Animal.js hosted with ❤ by GitHub

In the example above the privateVar field is not directly accessible.

As I switched to TypeScript a long time ago, I didn’t care too much and happily used the private keyword there.

	class Animal {
	private name: string;
	constructor(theName: string) {
	this.name = theName;
	}
	}

view raw Animal.ts hosted with ❤ by GitHub

Of course this was just a TypeScript hack and in the generated Javascript, the field was still accessible.

	"use strict";
	var Animal = /** @class */ (function () {
	function Animal(name) {
	this.name = name;
	}
	return Animal;
	}());

view raw Animal.js hosted with ❤ by GitHub

More recently I switched to a different syntax in TypeScript to specify private fields:

	class Animal {
	#name: string;
	constructor(name: string) {
	this.#name = name;
	}
	}

view raw Animal.ts hosted with ❤ by GitHub

What I wasn’t aware of that this became the default way that private fields are specified in Javascript.

	class Animal {
	#name
	constructor(name) {
	this.#name = name;
	}
	}

view raw Animal.js hosted with ❤ by GitHub

Cool!