Solution.js

// first array equivalent to rows 
let a = new Array(3);

// inner array equivalent to columns
for (i=0; i < a.length; i++) {
  a[i] = new Array(2);
}

// now assign values
a[0][0] = "1";
a[0][1] = "2";

a[1][0] = "1";
a[1][1] = "2";

a[2][0] = "1";
a[2][1] = "2";

let out = "";
for (let i=0; i < a.length; i++) {
  for (let j=0; j < a[i].length; j++) {
    out = out + a[i][j];
  }
}

console.log(out);