JavaScript · Beginner level

Beginner level · Module 3 of 5 · 10 guided hours

Arrays, Objects and Array Methods

Store collections in arrays and records in objects, transform data with map, filter and reduce, and read and write JSON.

Learning objectives

  • Create and modify arrays and objects
  • Transform data with map, filter, find and reduce
  • Convert between objects and JSON text

Topics

  • arrays and indexes
  • push, pop, slice, splice
  • objects and properties
  • destructuring
  • map, filter, find, reduce, sort
  • JSON.stringify and JSON.parse

Lessons

  1. Lesson 1 Arrays and Objects

    Store lists in arrays and records in objects, read and change them, and unpack them with destructuring.

    array index and lengthobject propertiesdot vs bracket notationdestructuring

  2. Lesson 2 Transforming Data with map, filter and reduce

    Use array methods to transform, select, find and summarise data without writing loops by hand.

    mapfilter and findreducesort with a compare function

  3. Lesson 3 JSON: Data as Text

    Convert objects to JSON text and back, the format used to store data and exchange it with servers.

    JSONJSON.stringifyJSON.parsetry/catch

Practical activity

Process a list of sales objects: add a total to each, keep sales above a threshold, sort them and sum the revenue.

Expected outcomes

  • Data handled as arrays of objects
  • Readable data transformations with array methods

Assessment

Practical: write five data transformations over a provided array of objects; marked by expected outputs.

Free taster lesson Arrays & Objects Read a free self-study lesson on this topic in the Free Course Library.

Taught live by an instructor — online or in person. Free course lessons are for self-study and do not lead to a certificate — see registration options.