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

# Reduce
Here, take each *element* of the **object** and convert the **array** of two **arrays** into an **array** of mutual users. 

// Reduce
function reducer (grouped_obj) {
    for (x in grouped_obj){
        var arr1 = grouped_obj[x][0];
        var arr2 = grouped_obj[x][1];
        // take intersection of the two and assign to property name x
        grouped_obj[x] = arr1.filter(i => arr2.indexOf(i) !== -1 
            && x.charAt(0) !== i
            && x.charAt(1) !== i
        )
    }
    return grouped_obj;
    // return an object {(man,friend): [Friends]}
}

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

console.log(reducer(grouped_obj));

In above code shows the **function `reducer`** which takes only one **argument**, `grouped_obj`. *Iterate* this **object** to *access* each nested **array** to **reduce** it to a **single array** of mutuals. For each **array** in **object**, call the **`filter` method** on either nested **arrays** (**line 7** to **10**). You can filter on either **array** to find the mutuals. Additionally, exclude any value equal to either member of the pair. The **`filter` method** output is *assigned* to the pair’s **property name**, overwriting the previous nested **array**.



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

Solution to Sub-task: Reduce

Reduce