Why Is Array/Object Destructuring So Useful And How To Use It (a JS example of destructuring shown in OCaml)

pattern_matching.ml

(*took examples from https://youtu.be/NIq3qLaHCIs*)

let printf = Printf.printf

let example1 = 
  let alphabet = ['a'; 'b'; 'c'; 'd'; 'e'; 'f'] in
  match alphabet with
  | a :: b :: _ ->
    printf "a = %c and b = %c\n" a b

let example2 = 
  let alphabet = ['a'; 'b'; 'c'; 'd'; 'e'; 'f'] in
  match alphabet with
  | a :: _ :: c :: rest ->
    printf "a = %c and c = %c\n" a c (*.. + use rest*)

let example3 = 
  let alphabet = ['a'; 'b'; 'c'; 'd'; 'e'; 'f'] in
  let numbers = [1; 2; 3; 4] in
  let new_list =
    [ alphabet |> List.map (fun v -> `Char v);
      numbers  |> List.map (fun v -> `Num v) ]
    |> List.flatten
  in new_list

let example4 =
  let sum_and_multiply a b = a + b, a * b in
  let sum, multiply = sum_and_multiply 2 3 in
  ()

type person = {
  name : string;
  age : int;
  address : address
}
and address = {
  city : string;
  state : string;
}

let example5 =
  let person_two = {
    name = "Sally";
    age = 32;
    address = {
      city = "Somewhere else";
      state = "Another one of them";
    }
  }
  in
  let { name; age } = person_two in
  () (*...*)

let example6 =
  let person_two = {
    name = "Sally";
    age = 32;
    address = {
      city = "Somewhere else";
      state = "Another one of them";
    }
  }
  in
  let { name = first_name; age } = person_two in
  printf "first name = %s\n" first_name

let example7 =
  let person_two = {
    name = "Sally";
    age = 32;
    address = {
      city = "Somewhere else";
      state = "Another one of them";
    }
  }
  in
  let { name = first_name; address = { city }} = person_two in
  printf "city = %s\n" city

let example8 =
  let person_two = {
    name = "Sally";
    age = 32;
    address = {
      city = "Somewhere else";
      state = "Another one of them";
    }
  }
  in
  let print_user { name; age } = 
    printf "name is %s and age is %d\n" name age
  in
  print_user person_two