JavaScript is the de facto language for building modern web and mobile applications. It powers a wide range of projects, from simple websites to dynamic, interactive apps.

To create products that users will love and appreciate, it's essential you write code that is not only functional but also efficient and easy to maintain. Clean JavaScript code is vital for the success of any web or mobile app, whether it's a hobby side project or a complex commercial application.

What’s So Good About JavaScript Functions?

A function is an essential component for writing code any application. It defines a chunk of reusable code that you can invoke to perform a specific task.

Beyond their reusability, functions are highly versatile. In the long run, they simplify the process of scaling and maintaining a codebase. By creating and using JavaScript's functions, you can save a lot of development time.

Here are some helpful JavaScript functions that can significantly improve the quality of your project's code.

1. once

This higher-order once function wraps another function to ensure you can only call it a single time. It should silently ignore subsequent attempts to call the resulting function.

Consider a situation where you want to make HTTP API requests to fetch data from a database. You can attach the once function as a callback for an event listener function, so that it triggers once, and no more.

Here's how you might define such a function:

        const once = (func) => {
    let result;
    let funcCalled = false;

    return (...args) => {
        if (!funcCalled) {
            result = func(...args);
            funcCalled = true;
        }

        return result;
    };
};

The once function takes a function as an argument and returns a new function that you can only call once. When you call the new function for the first time, it runs the original function with the given arguments and saves the result.

Any subsequent calls to the new function return the saved result without running the original function again. Take a look at the implementation below:

        // Define a function to fetch data from the DB
function getUserData() {
    // ...
}

// get a version of the getUserData function that can only run once
const makeHTTPRequestOnlyOnce = once(getUserData);
const userDataBtn = document.querySelector("#btn");
userDataBtn.addEventListener("click", makeHTTPRequestOnlyOnce);

By using the once function you can guarantee the code only sends one request, even if the user clicks the button several times. This avoids performance issues and bugs that may result from redundant requests.

2. pipe

This pipe function lets you chain multiple functions together in a sequence. The functions in the sequence will take the result of the preceding function as the input and the last function in the sequence will compute the final result.

Here is an example in code:

        // Define the pipe function
const pipe = (...funcs) => {
   return (arg) => {
       funcs.forEach(function(func) {
           arg = func(arg);
       });

       return arg;
   }
}

// Define some functions
const addOne = (a) => a + 1;
const double = (x) => x * 2;
const square = (x) => x * x;

// Create a pipe with the functions
const myPipe = pipe(addOne, double, square);

// Test the pipe with an input value
console.log(myPipe(2)); // Output: 36

Pipe functions can improve the readability and modularity of code by allowing you to write complex processing logic concisely. This can make your code more understandable, and easier to maintain.

3. map

The map function is a method of the built-in JavaScript Array class. It creates a new array by applying a callback function to each element of the original array.

It loops through each element in the input array, passes it as an input to the callback function, and inserts each result into a new array.

What's important to note is that the original array is not modified in any way throughout this process.

Here's an example of how to use map:

        const numbers = [1, 2, 3, 4, 5];

const doubledNumbers = numbers.map(function(number) {
    return number * 2;
});

console.log(doubledNumbers);
// Output: [2, 4, 6, 8, 10]

In this example, the map function iterates over each element in the numbers array. It multiplies each element by 2 and returns the results in a new array.

Generally, map functions eliminate the need for using loops in JavaScript, especially infinite ones—infinite loops can cause significant computational overhead, leading to performance issues in an application. This makes the codebase more concise and less error-prone.

4. pick

This pick function lets you selectively extract specific properties from an existing object and generate a new object with those properties as the result of the computation.

For instance, consider a reports feature in an application, by utilizing the pick function, you can effortlessly customize different reports based on the desired user information by explicitly specifying the properties that you want to include in various reports.

Here's an example in code:

        const pick = (object, ...keys) => {
    return keys.reduce((result, key) => {
        if (object.hasOwnProperty(key)) {
            result[key] = object[key];
        }

        return result;
    }, {});
};

The pick function takes an object and any number of keys as arguments. The keys represent the properties you want to select. It then returns a new object that contains only the properties of the original object with matching keys.

        const user = {
    name: 'Martin',
    age: 30,
    email: 'Martin@yahoo.com',
};

console.log(pick(user, 'name', 'age'));
// Output: { name: 'Martin', age: 30 }

Essentially, a pick function can encapsulate complex filtering logic into a single function, making the code easier to understand and debug.

It can also promote code reusability, since you can reuse the pick function throughout your codebase, reducing code duplication.

5. zip

This zip function combines arrays into a single array of tuples, matching corresponding elements from each input array.

Here's an example implementation of a zip function:

        function zip(...arrays) {
    const maxLength = Math.min(...arrays.map(array => array.length));

    return Array.from(
       { length: maxLength },
       (_, index) => arrays.map(array => array[index])
   );
};

const a = [1, 2, 3];
const b = ['a', 'b', 'c'];
const c = [true, false, true];

console.log(zip(a, b, c));
// Output: [[1, 'a', true], [2, 'b', false], [3, 'c', true]]

The zip function accepts input arrays and calculates their longest length. It then creates and returns a single array using the Array.from JavaScript method. This new array contains elements from each input array.

This is especially useful if you need to combine data from multiple sources instantly, removing the need to write redundant code that would otherwise clutter your codebase.

Working With JavaScript Functions in Your Code

JavaScript functions greatly improve the quality of your code by providing a simplified and compact way to handle a lot of the programming logic for both small and large codebases. By understanding and using these functions, you can write more efficient, readable, and maintainable applications.

Writing good code makes it possible to build products that not only solve a particular problem for end users, but do so in a way that's easy to modify.