What is the map.keys() method in TypeScript?
Overview
A map, also known as a dictionary, is a data structure that is made up of key-value pairs. Each entry of the map contains a key-value pair. We can use the keys() method to get all the keys of the map.
Syntax
Map.keys()
The syntax for map.keys() in TypeScript
Parameters
Map: This is the set whose keys' iterators we want to get.
Return value
It returns a Map iterator.
Example
// Create some mapslet evenNumbers = new Map<string, number>([["two", 2], ["four", 4], ["eight", 8]])let cart = new Map<string, number>([["rice", 500], ["bag", 10]])let countries = new Map<string, string>([["NG", "Nigeria"], ["BR", "Brazil"], ["IN", "India"]])let isMarried = new Map<string, boolean>([["James", false], ["Jane", true], ["Doe", false]])let emptyMap = new Map<null, null>()// get the iteratorslet itr1 = evenNumbers.keys()let itr2 = cart.keys()let itr3 = countries.keys()let itr4 = isMarried.keys()let itr5 = emptyMap.keys()// log out the iteratorsconsole.log(itr1)console.log(itr2)console.log(itr3)console.log(itr4)console.log(itr5)// log out values for any of the iteratorsfor (let value of itr1) {console.log(value);}
Explanation
- Lines 2–6: We create some maps in TypeScript.
- Lines 9–13: We use the
keys()method to get the iterators of the created sets. - Lines 16–20: We log the iterators to the console.
- Lines 23-25: We use the
for ofloop to iterate over one of the iterators. Next, we print its values to the console.