how to use upshift js code example

Example 1: prepend to js array

var a = [1, 2, 3, 4];
a.unshift(0);
a; // => [0, 1, 2, 3, 4]

Example 2: .unshift

let monTableau = ['un', 'deux','trois', 'quatre'] ;
monTableau.unshift('zero') ; 
//console.log(monTableau) ;
 
 

 let monTableau2D = [
     ['Mark' , 'jeff' , 'Bill'] , 
     ['Zuckerberg' , 'Bezos' , 'Gates']
 ] ;
 monTableau2D[1].unshift('test') ; 
 //console.log(monTableau2D) ;