Underscore Js Create A Map Out Of List Of Objects Using A Key Found In The Object

Imagine you have a list of objects and you want to create a map out of them using a specific key found in each object. This is where Underscore.js comes to the rescue! Underscore.js is a handy library that provides a lot of useful functions to manipulate data in JavaScript effortlessly.

To create a map out of a list of objects using a key found in each object, we can utilize Underscore.js's `_.indexBy` function. This function allows us to index a collection of objects by some key, providing a quick and efficient way to access and work with the data.

Here's a simple example to demonstrate how to achieve this using Underscore.js:

const listOfObjects = [
    { id: 1, name: 'Alice' },
    { id: 2, name: 'Bob' },
    { id: 3, name: 'Charlie' }
];

const key = 'id';

const mapByKey = _.indexBy(listOfObjects, key);

console.log(mapByKey);

In the above code snippet, we have a list of objects `listOfObjects` where each object has an `id` key. We use the `_.indexBy` function to create a map called `mapByKey` where the objects are indexed by their `id` values.

By running this code, you will see the output similar to:

{
    "1": { "id": 1, "name": "Alice" },
    "2": { "id": 2, "name": "Bob" },
    "3": { "id": 3, "name": "Charlie" }
}

This output demonstrates how Underscore.js has efficiently created a map based on the `id` key from our list of objects.

Additionally, you can also specify a custom function to derive the key from each object. For example, if the key you want to index by is nested inside the object structure, you can achieve it by passing a custom iteratee function to `_.indexBy`.

const mapByNestedKey = _.indexBy(listOfObjects, obj => obj.nestedObj.key);

console.log(mapByNestedKey);

In the above code snippet, `nestedObj` is a nested object within each object in `listOfObjects`, containing the `key` we want to use for indexing. By specifying the custom `obj => obj.nestedObj.key` function, Underscore.js will index the objects based on the `key` inside the nested object.

With Underscore.js's `_.indexBy` function, creating a map out of a list of objects using a key found in the object is made simple and efficient. This powerful feature can greatly enhance your data manipulation capabilities in JavaScript.

So, next time you need to quickly organize your data into a map structure, remember that Underscore.js has got your back! Happy coding!