Objects

What is a JS Object?

• Unordered key-value pairs
• Work well when you don't need order
• Work well you when you need fast access/insertion and removal

Big O of Object Operations

• Insert - O(1)
• Delete - O(1)
• Search - O(N)
• Read - O(1)

Big O of Object Methods

• Object.keys - O(N)

• Object.values - O(N)

• Object.entries - O(N)

• hasOwnProperty - O(1)

Arrays

What is an array?

• Ordered list of index-value pairs
• Good for when you need order

Big O of Array Operations

• Insert - depends...
  • Inserting at the end of an array is simply 1 step
  • Inserting at the beginning of an array of N length takes N steps because you have to shift/re-index each value that comes after the insertion
• Delete - depends...
  • Deleting at the end of an array is simply 1 step
  • Deleting at the beginning of an array of N length takes N steps because you have to shift/re-index each value that comes after the deletion
• Search - O(N)
• Read - O(1)

Big O of 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 * _logN)
• forEach/map/filter/reduce/etc. - O(N)