JS.06.01 Mid-level

Property descriptors, freeze and seal

Comes up in: JavaScript

This concept is being written. It gets the full five steps — explanation, predict, interview angle, practice with tests, and review cards. Here is exactly what it will cover, so you can study it elsewhere in the meantime.

What it covers

writable/enumerable/configurable
accessor properties
Object.defineProperty
freeze (shallow) vs seal vs preventExtensions
property order rules (integer keys first)

Words you will know

property descriptoraccessorfreezeseal

What you will practise

deepFreeze
predict key order

Interview questions this answers

Does Object.freeze make an object deeply immutable?
In what order are object keys iterated?