Destructuring arrays

  1. var nums = [1, 2, 3, 4, 5];
  3. var [first, second,,,,fifth] = nums;
  4. log(first, second, fifth); // 1, 2, 5

Swapping variables

how to swap variables without using a temp var

  1. var a = 1, b = 2;
  3. // The Old Way
  4. var temp = a, a = b, b = tmep;
  6. // The New Way
  7. [b, a] = [a, b];

Method signature

  1. var nums = [1, 2, 3, 4];
  2. doSomething(nums);
  4. function doSomething([first, second, ...others]){
  5.   log(first);   //logs 1
  6.   log(second);  //logs 2
  7.   log(others);  //logs [3, 4]
  8. }

Nested Destructuring Array

  1. var nums = [1, 2, [30, 40, [500, 600]]];
  3. var [one,,[thirty,,[,sixhundert]]] = nums;

Pattern Errors

  1. let [x] = [2, 3]    // x = 2
  2. let [x] = {'0': 4}  // x = 4
  3. let [x, y, z] = [1, 2]  // throw

Refutable

  1. // Entire Pattern is Refutable
  2. let ?[x, y, z] = [1, 2]  // x = 1, y = 2, z = undefined
  4. // Only 'z' is Refutable
  5. let [x, y, ?z] = [1, 2]  // z = 1, y = 2, z = undefined