JS: Array.prototype.map

xArray.map(f)

• Apply function to every element of the array.
• Return the new array.
• Original array is not changed.

f is passed 3 args: currentElement currentIndex xArray.

const aa = [3, 4, 5];
const bb = aa.map((x) => (x + 1));

console.log(bb); // [ 4, 5, 6 ]

// original is not changed
console.log(aa); // [ 3, 4, 5 ]

xArray.map(f, thisArg)

Use thisArg for this (binding) of f. Default to undefined.

// example of using map with second argument
function ff(x) {
  return [x, this];
}
console.log([3, 4, 5].map(ff, 9));
// [ [ 3, 9 ], [ 4, 9 ], [ 5, 9 ] ]