map Size in JavaScript - ECMAScript 2021

To get the size of a hash (object) in JavaScript - ECMAScript 2021, we can use the Object.keys() method to convert the hash into an array of keys, and then use the length property to determine the size of the array.

Here's an example:

const myHash = { 
  firstKey: "value1", 
  secondKey: "value2", 
  thirdKey: "value3" 
};
const size = Object.keys(myHash).length;
console.log(size); // Output: 3

In this example, we define a hash called myHash with three key-value pairs. We then call Object.keys() on myHash to get an array of its keys, and find its length using the length property. We store the length in a variable called size, and finally output the value of size to the console.

Note that this method will only work for hashes that have keys that are strings or symbols. If your hash has keys that aren't strings or symbols, the Object.keys() method won't work and you'll need to use a different approach.