How to Map a TypeScript Array (or List)

AUGUST 28, 2018

In TypeScript, as in other languages, Array.map allows you to apply a function to each of the items on a list or array. You can either pass an existing function which will take each of the items as its input parameter (say, the existing Math.sqrt function, or one that you define).

let list = [0, 1, 2, 3]; // [0, 1, 2, 3]
list.map(Math.sqrt); // [ 0, 1, 1.414.., 1.732.. ]

Or you can also define a lambda function on-the-go.

let list = [0, 1, 2, 3]; // [0, 1, 2, 3]
list.map((value, key, all) => {
  list[key] = value * 2;
}); // [ 0, 2, 4, 6]

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