Explore the basics of JavaScript in greater detail to solve real-world problems.

Zero to Hero in JavaScript

This module aims to teach us how to write cleaner, more modular, and more scalable code in JavaScript by giving us an understanding of object-oriented programming (OOP). We'll start with the basics of object-oriented programming and build up to more advanced concepts such as data protection and inheritance. Along the way, we'll learn how each concept applies to JavaScript in particular, as well as how various JavaScript features make it a suitable language for object-oriented programming.

JavaScript: A Deep Dive

# Group

**Group** all elements of the **array** into a single **object**.

// Group
function group (mapped_arr) {
    var obj = {}
    mapped_arr.forEach(x => {
        var key = Object.keys(x)[0]; // assign person 
        if (key in obj){
            // push all elements of x[key] into obj[key]
            obj[key].push(Array.from(x[key]));    
        }
        else {
            // Assign copy of the array to the object with key 
            obj[key] = [Array.from(x[key])];
        }
    })
    return obj;
    // return an object {(man,friend): [Friends]}
}

var mapped_arr = [
    { 'AB': [ 'B', 'C', 'D' ] },
    { 'AC': [ 'B', 'C', 'D' ] },
    { 'AD': [ 'B', 'C', 'D' ] },
    { 'AB': [ 'A', 'C', 'D', 'E' ] },
    { 'BC': [ 'A', 'C', 'D', 'E' ] },
    { 'BD': [ 'A', 'C', 'D', 'E' ] },
    { 'BE': [ 'A', 'C', 'D', 'E' ] },
    { 'AC': [ 'A', 'B', 'D', 'E' ] },
    { 'BC': [ 'A', 'B', 'D', 'E' ] },
    { 'CD': [ 'A', 'B', 'D', 'E' ] },
    { 'CE': [ 'A', 'B', 'D', 'E' ] },
    { 'AD': [ 'A', 'B', 'C', 'E' ] },
    { 'BD': [ 'A', 'B', 'C', 'E' ] },
    { 'CD': [ 'A', 'B', 'C', 'E' ] },
    { 'DE': [ 'A', 'B', 'C', 'E' ] },
    { 'BE': [ 'B', 'C', 'D' ] },
    { 'CE': [ 'B', 'C', 'D' ] },
    { 'DE': [ 'B', 'C', 'D' ] } 
];

console.log(group(mapped_arr));

In the code above, the **function `group`** takes only one **argument**: `mapped_arr`. The elements are **grouped** by first *iterating* the **array** *assigned* to `mapped_arr`. Because **objects** only have one element, call the **method** `Object.keys()` on each **object** and *index* the first element (**line 5**). Use the extracted **key** to create a new **property** in the final **object** *assigned* to `obj`, if it does not exist. The value of the **object** is pushed into the **array** *assigned* to the corresponding **key** in the final **object**. Repeating this step for all **objects** of `mapped_arr` gives us **grouped** representation in the final **object** (`obj`).


The solution to the Sub-task "Group" for the project "Find Mutual Friends"

Solution to Sub-task: Group

Group