JSFiddle - React, Tailwind, and code Playground

JavaScript

var a = [ 
		[1, 2],
		[3, {x: 5}]
	],
	b = a.slice(),
	c = cloneDeep(a);

a[1][1].x = 9;

function cloneDeep(mas) {
  var masClone = Array.isArray(mas) ? new Array(mas.length) : {};   
  
  Object.keys(mas).forEach(function (key) {
    if (Array.isArray(mas[key]) || Object.prototype.toString.call(mas[key]) === "[object Object]")
      masClone[key] = cloneDeep(mas[key]);
    else
      masClone[key] = mas[key];
  });

  return masClone;
}

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