Object literal: computed properties

Object literal properties may be computed values

a computed property x needs to be surrounded by []

const propertyName = 'x'; const obj = {propertyName: 1}; assert.equal(obj.x, 1);

can also get a function assigned

const key = 'func'; const obj = {[key]: 'seven'}; assert.equal(obj.func(), 'seven');

the key may also be the result of a function call

const getName = () => 'propertyName'; const obj = {[getName]() {return 'seven'}}; assert.equal(obj.propertyName(), 'seven');

the key can also be constructed by an expression

const what = 'Key'; const obj = {['proper' + what]: null}; assert('propertyName' in obj);

accessor keys can be computed names too

const obj = { set ['key'](_) {return 1}, }; assert.equal(obj.key, 1);

Required Knowledge

• basics (Arrow functions)
• `const` declaration (Block scope)
• basics (Object literal)

Related Katas

Global Object API

• parseInt()

Object API

• Object() (as introduced in ES1)
• Object.is()
• Object.fromEntries()
• Object.fromEntries() in depth

Object literal

• basics
• computed properties
• getter
• setter

Difficulty Level

ADVANCED

First Published

3 April 2015

Stats

5 tests to solve