JSFiddle - React, Tailwind, and code Playground

JavaScript

var a = [ 
		[1, 2],
		[3, [5]]
	],
	b = a.slice(),
	c = cloneArray(a);

a[1][1][0] = 9;

function cloneArray(mas) {
	var masClone = new Array(mas.length);

	mas.forEach(function (item, key) {
		if (Array.isArray(item)) {
			masClone[key] = cloneArray(item);
		} else {
			masClone[key] = item;
		}
	});

	return masClone;
}

console.log(a[1][1][0], b[1][1][0], c[1][1][0]);