martincartledge.github.io

analyzing performance of arrays and objects

objects

• unordered, key value pairs
• when you don’t need order
• when you need fast access for insertion and removal
  • insertion O(1)
  • removal O(1)
  • searching O(n)
  • access O(1)
• object methods
  • Object.keys() O(n)
  • Object.values() O(n)
  • Object.entries() O(n)
  • hasOwnProperty() O(1)

arrays

• ordered lists
• use when you need order
• when you need access for insertion and removal
  • insertion at end (push) O(1)
  • insertion anywhere else (unshift) O(n)
  • removal at end (pop) O(1)
  • removal anywhere else (shift) O(n)
  • searching O(n)
  • access O(1)
  • array methods
    • push O(1)
    • pop O(1)
    • shift O(n)
    • unshift O(n)
    • concat O(n)
    • slice O(n)
    • splice O(n)
    • sort O(n * log n)
    • forEach, map, filter, reduce O(n)