JavaScript Map & Set
5 lessonsAbout 30 minutesAdvanced
This part of the JavaScript Tutorial runs from JavaScript Map through to JavaScript WeakMap and WeakSet. There are 5 lessons here, and working through them takes about 30 minutes at a steady pace.
It follows on from JavaScript Errors, so finish that first if you have not already — the examples below assume you are comfortable with it.
Each lesson below says what it covers before you open it. Read them in order the first time; afterwards this page works as a index you can jump back into when you need to check one thing.
- 1JavaScript MapA Map stores key and value pairs where the key can be any type.
- 2JavaScript Map MethodsMap methods let you loop over entries and convert to and from other structures.
- 3JavaScript SetA Set stores unique values, automatically ignoring duplicates.
- 4JavaScript Set OperationsSets can be combined to find values in common, or values in one but not the other.
- 5JavaScript WeakMap and WeakSetWeakMap and WeakSet hold objects without preventing them being cleaned up.