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Array and Objects

A brief description BUILT-IN DATA STRUCTURES Through the lens of Big O Notation.

OBJECTIVES

  • Understand how objects and arrays work, through the lens of Big O
  • Explain why adding elements to the beginning of an array is costly
  • Compare and contrast the runtime for arrays and objects, as well as built-in methods

OBJECTS

Unordered, key value pairs!

let instructor = {
    firstName: "Kelly",
    isInstructor: true,
    favoriteNumbers: [1,2,3,4]
}

When to use objects?

  • When you don't need order
  • When you need fast access/insertion and removal

Big O of Objects

Insertion - O(1)

Removal - O(1)

Searching - O(N)

Access - O(1)

When you don't need any ordering, objects are an excellent choice!

Big O of Object Methods

Object.keys - O(N)

Object.values - O(N)

Object.entries - O(N)

hasOwnProperty - O(1)

ARRAYS

Ordered lists!

let names = ["Michael", "Melissa", "Andrea"];

let values = [true, {}, [], 2, "awesome"];

WHEN TO USE ARRAYS?

  • When you need order
  • When you need fast access / insertion and removal (sort of....)

Big O of Arrays

Insertion - It depends....

Removal - It depends....

Searching - O(N)

Access - O(1)

Let's see what we mean by that!

Big O of Array Operations

  • 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/etc. - O(N)

Limitations of Arrays

Inserting at the beginning is not as easy as we might think! There are more efficient data structures for that!