JS: Maps can store any type of key

const myMap = new Map([]);

const numberKey = 1;
const stringKey = "str";
const arrayKey = [1, 2, 3];
const objectKey = { name: "abc" };

myMap.set(numberKey, "Number Key");
myMap.set(stringKey, "String Key");
myMap.set(arrayKey, "Array Key");
myMap.set(objectKey, "Object Key");

myMap.forEach((value, key) => console.log(`${key} : ${value}`));

/*
Output:
1 : Number Key
str : String Key
1,2,3 : Array Key
[object Object] : Object Key
*/

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Comments

[Tobias Nickel]

yes, it is very good to store meta data about objects, without modifying the object. I think you will love WeakMap for that.