How to conditionally build an object in JavaScript with ES6

by Janeth Kent Date: 09-08-2019 javascript coding ES6


The arrival of ES6 brought us, among many other news, the spread syntax, which, as you will already know, allows us to save a few lines of code and improve legibility.

Specifically, this syntax allows us to destructure the parameters that we pass to a function so that our code goes from:

function foo(data) {
const id = data.id
const title = data.name
// more...
}

to

function foo({id, title}) {
//more
}

But also thanks to the operator spread ... , we can expand (unwrap) objects in order to perform operations such as:

const obj1 = {a: 1, b: 2};
const obj2 = {...obj1, c: 3};
// obj2 = {a: 1, b: 2, c: 3};

However, another implementations of this syntax is to create objects with certain properties dependent on a condition, which is what I wanted to talk about in this article.

For example, if we have the following code:

const obj1 = {a: 1, b: 2};
if (condition) {
ob1.c = 3;
}
if (otherCondition) {
obj.d = 4;
}const obj1 = {a: 1, b: 2};
if (condition) {
ob1.c = 3;
}
if (otherCondition) {
obj.d = 4;
}

By using the spread syntax we can transform it into the following, much more readable:

const obj1 = {
a: 1, 
b: 2,
...(condition ? {c:3} : {}),
...(otherCondition ? {c:4} : {})
};

This is possible because the operator only acts if the condition is true. Remember that if you are going to use this way of creating objects, 0 evaluates to false so you should perform a strict check.

As you can see, using this operator allows us to improve our code a lot and get rid of those annoying ifs we had to add if we wanted to achieve something similar.

 
by Janeth Kent Date: 09-08-2019 javascript coding ES6 hits : 10285  
 
Janeth Kent

Janeth Kent

Licenciada en Bellas Artes y programadora por pasión. Cuando tengo un rato retoco fotos, edito vídeos y diseño cosas. El resto del tiempo escribo en MA-NO WEB DESIGN END DEVELOPMENT.

 
 
 

Related Posts

Node.js and npm: introductory tutorial

In this tutorial we will see how to install and use both Node.js and the npm package manager. In addition, we will also create a small sample application. If you…

How to connect to MySQL with Node.js

Let's see how you can connect to a MySQL database using Node.js, the popular JavaScript runtime environment. Before we start, it is important to note that you must have Node.js installed…

JavaScript Programming Styles: Best Practices

When programming with JavaScript there are certain conventions that you should apply, especially when working in a team environment. In fact, it is common to have meetings to discuss standards…

Difference between arrow and normal functions in JavaScript

In this tutorial we are going to see how arrow functions differ from normal JavaScript functions. We will also see when you should use one and when you should use…

JavaScript Arrow functions: What they are and how to use them

In this article we are going to see what they are and how to use JavaScript Arrow Functions, a new feature introduced with the ES6 standard (ECMAScript 6). What are Arrow…

How to insert an element into an array with JavaScript

In this brief tutorial you will learn how to insert one or more elements into an array with JavaScript. For this we will use the splice function. The splice function will not…

What is the difference between primitives types and objects in JavaScript?

In this short tutorial we are going to look at the differences between primitive types and objects in JavaScript. To start with, we're going to look at what primitive types…

How to get DOM elements with JavaScript

When you access any element of the DOM, it is usual to save it in a variable. This is something that at first might seem very simple, but if you…

How to reverse an array in JavaScript

In this tutorial we are going to see how you can change the order of the elements of an array so that they are inverted. You could use a loop…

How synchronize the scroll of two divs with JavaScript

In case you have two divs of different sizes you may sometimes want to scroll both at the same time but at different speeds depending on their size. For example,…

How to use the codePointAt method in JavaScript

The JavaScript codePointAt method has more or less the same function as the charCodeAt method, used to get the 16-bit Unicode representation of the character at a certain position in…

How to check if a value is a number in JavaScript

In this short tutorial we are going to look at the various methods that exist to find out if a value is a number in JavaScript.   1. Using the isNaN() function   One…

We use our own and third-party cookies to improve our services, compile statistical information and analyze your browsing habits. This allows us to personalize the content we offer and to show you advertisements related to your preferences. By clicking "Accept all" you agree to the storage of cookies on your device to improve website navigation, analyse traffic and assist our marketing activities. You can also select "System Cookies Only" to accept only the cookies required for the website to function, or you can select the cookies you wish to activate by clicking on "settings".

Accept All Only sistem cookies Configuration