Object literal: setter

An object literal can also contain setters

defining: a setter

by prefixing the property with set (and make it a function)

let theX = null; const obj = { x(newX) { theX = newX; } }; obj.x = 'the new X'; assert.equal(theX, 'the new X');

must have exactly one parameter

let setterCalledWith = void 0; const obj = { x() { // <<<<=== it's not a setter yet! if (arguments.length === 1) { setterCalledWith = arguments[0]; } } }; assert.equal(obj.x = 'new value', setterCalledWith);

can be a computed property (an expression enclosed in [])

const publicPropertyName = 'x'; const privatePropertyName = '_' + publicPropertyName; const obj = { [privatePropertyName]: null, // write the complete setter to make the assert below pass :) }; obj.x = 'axe'; assert.equal(obj._x, 'axe');

working with/on the setter

you can use delete to remove the property (including it`s setter)

let setterCalled = false; const obj = { set x(param) { setterCalled = true; } }; // delete the property x here, to make the test pass obj.x = true; assert.equal(setterCalled, false);

Links

mdn docs Description of all the details of a setter.
spec "An accessor property associates a key value with one or two accessor functions ..."
spec The syntax definition of how to write an (accessor) method.
announcement Announcement of this kata on twitter.

Required Knowledge

• `let` declaration (Block scope)
• `const` declaration (Block scope)
• basics (Object literal)
• computed properties (Object literal)

Related Katas

Global Object API

• parseInt()

Object API

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

Object literal

• basics
• computed properties
• getter
• setter

Difficulty Level

BEGINNER

First Published

28 July 2015

Stats

4 tests to solve