Javascript few useful array methods to use without accidentally touching the Array.prototype and create a possible conflict

extend-array.js

class List extends Array {
	constructor() {
		super(...arguments);
	}

	uniq() {
		return [... new Set(this)];
	}

	empty() {
		return this.length = 0;
	}

	flatten() {
		return this
		.toString()
		.split(',')
		.reduce( (a,c) => {
			let i = parseFloat(c);
			c = (!Number.isNaN(i)) ? i : c;
			a.push(c);
			return a;
		}, []);
	}

	tupl() {
		return Object.freeze(this);
	}
};

console.log(List.prototype.flatten.call([[1,2,3],4,5,"h","e",["l","l","o"], 3.75])); 
// outputs - [1, 2, 3, 4, 5, "h", "e", "l", "l", "o", 3.75]