map() – JavaScript Functional Programming

What is functional programming?

Functional programming is a programming paradigm, the process of building components using pure functions and avoiding shared state, mutable data and side-effects.

In simple, functional programming is doing our tasks with functions, avoiding side effects by using pure functions.

For example, Without iterating the list using user defined loops; we can iterate the list using the functions like map(), reduce(), and filter()

Lets see about map() function in this post.

I have started exploring about functional programming in recent times. The topic looks very interesting and helping me to optimize my own codes. After using functional programming, my code looks pretty good and maintainable.

For example, If I need to iterate a list and extract some data previously I use some for loops to do the task like following:

var players = [
 { name: 'Dhoni', nickname: 'Super Cool Captain' },
 { name: 'Raina', nickname: 'Furious fielder' },
 { name: 'Ashwin', nickname: 'Spin Master' }
];

var namelistusingloop = [];

for (var i = 0; i < players.length; i++) {
 namelistusingloop.push(players[i].name);
}

Later I found that using map function, we can simplify our function even more.

map() will take callback function as follows.

var namelistusingmap = players.map(function (player) {
 return player.name;
});

In the above part, the map() will iterate the list based on its length. We don’t have to initialize & iterate list as we did in the for loop.

Now the code looks simple and effective. All the short code doesn’t mean effective, unless it reduce the development time & maintenance period.

We can even simplify the code with map() using arrow functions.

var namelistwitharrow = players.map((player) => player.name);

In short, arrow function is used to simplify our callback function. To know more about arrow functions click here to visit earlier post in this space.

Now the code looks even cooler and smart

var namelistusingmap = players.map(function (player) {
 return player.name;
});

var namelistwitharrow = players.map((player) => player.name);

Lets put all code together to compare to take quick look,

var players = [
 { name: 'Dhoni', nickname: 'Super Cool Captain' },
 { name: 'Raina', nickname: 'Furious fielder' },
 { name: 'Ashwin', nickname: 'Spin Master' }
];

// using loops
var namelistusingloop = [];

for (var i = 0; i < players.length; i++) {  namelistusingloop.push(players[i].name); } // using map function var namelistusingmap = players.map(function (player) {  return player.name; }); // using map function and arrow function var namelistwitharrow = players.map((player) => player.name);

console.log(namelistusingloop);
console.log(namelistusingmap);
console.log(namelistwitharrow);


Output

["Dhoni", "Raina", "Ashwin"]
["Dhoni", "Raina", "Ashwin"]
["Dhoni", "Raina", "Ashwin"]

Now its up to us to decide which module we have to use in our code – the code using pure function or using the loops.

Lets explore more about functional programming in upcoming posts.

Happy coding!

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