Typescript Map Explained

Last update: 2022-12-01
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To create a Map in TypeScript, you can use the Map constructor.

const map = new Map<string, number>();

This creates a new Map object that is empty. You can then add key-value pairs to the map using the set method.

map.set('one', 1);
map.set('two', 2);

You can also create a Map and add key-value pairs to it in a single step using an array of tuples.

const map = new Map<string, number>([
	['one', 1],
	['two', 2]
]);

You can then access the values in the map using the get method, and check if a key is in the map using the has method.

console.log(map.get('one')); // outputs 1
console.log(map.has('two')); // outputs true

There are a few reasons you might want to use a Map in TypeScript instead of a regular object:

  1. Type safety: When you use a Map, you can specify the types of the keys and values that it will contain. This can help prevent errors caused by trying to access properties with the wrong type.

  2. Iteration order: A Map maintains the order in which key-value pairs are added, so you can be sure that the key-value pairs will be iterated over in the same order that they were added. This is not the case with regular objects, whose properties are iterated over in a arbitrary order.

  3. Methods: A Map has built-in methods for adding, deleting, and accessing key-value pairs, which can make it easier to work with compared to using a regular object.

That being said, there are also situations where it might be more appropriate to use a regular object. For example, if you don’t need the features mentioned above and you just need a simple key-value store, a regular object might be sufficient.

Simon Grimm

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