JSFiddle - React, Tailwind, and code Playground

JavaScript

var tab = [ [10, 20], [11, 21] ];
for(i=0; i<tab.length; i++)
    alert(tab[i][1]);
var z = "[ [10, 20], [11, 21] ]";
var y = eval('(' + z + ')');
var tablica = {};
for(i=0; i<y.length; i++) {
    alert(y[i][1]);
    tablica[i] = { 'a':y[i][0], 'b':y[i][1] };
}    
alert(tablica[1].a);