Javascript array cheatsheet

A cheatsheet of array methods:

• To add/remove elements:
  • push(...items) – adds items to the end,
  • pop() – extracts an item from the end,
  • shift() – extracts an item from the beginning,
  • unshift(...items) – adds items to the beginning.
  • splice(pos, deleteCount, ...items) – at index pos delete deleteCount elements and insert items.
  • slice(start, end) – creates a new array, copies elements from position start till end (not inclusive) into it.
  • concat(...items) – returns a new array: copies all members of the current one and adds items to it. If any of itemsis an array, then its elements are taken.
• To search among elements:
  • indexOf/lastIndexOf(item, pos) – look for item starting from position pos, return the index or -1 if not found.
  • includes(value) – returns true if the array has value, otherwise false.
  • find/filter(func) – filter elements through the function, return first/all values that make it return true.
  • findIndex is like find, but returns the index instead of a value.
• To transform the array:
  • map(func) – creates a new array from results of calling func for every element.
  • sort(func) – sorts the array in-place, then returns it.
  • reverse() – reverses the array in-place, then returns it.
  • split/join – convert a string to array and back.
  • reduce(func, initial) – calculate a single value over the array by calling func for each element and passing an intermediate result between the calls.
• To iterate over elements:
  • forEach(func) – calls func for every element, does not return anything.
• Additionally:
  • Array.isArray(arr) checks arr for being an array.

Please note that methods sort, reverse and splice modify the array itself.