Understanding React's Declarative Programming Paradigm

Understanding React's Declarative Programming Paradigm

Recently I’ve spent some time learning more about the React ecosystem. A programming paradigm that often leaves newcomers puzzled when starting is understanding what is the difference between imperative and declarative programming.

We always hear about React being declarative but what does that mean? It’s one of the first things you’re taught when learning React. It’s just brushed over as something that only makes sense after you know it.

Let’s take a look at the definition of declarative programming, it is essentially “telling a computer what to do”. You’re probably thinking at this point that you’ve always been telling a computer what to do each time you type code. This idea is true, to an extent.

Although the definition of imperative programming does not add much clarity, doing it with imperative programming which is telling a computer how to do something, you now have an excellent combination.

We have learned two things so far. Declarative programming is something that you tell a computer "what to do". And imperative programming is something you tell a computer “how to do it”.

Once again, these definitions lack a little detail, but I believe if we go further into this topic with the combination of code samples and analogies, we can find an effective way to explain it all.



In order to make lemonade, I will add ½ cup of lime juice and 1 cup of sugar to a half-gallon jug of water then stir until fully mixed. I will then get a glass filled with ice and pour some lemonade into the glass to drink.


I want a glass of lemonade.

The difference between these two analogies is that with the imperative way, you’re more focused on how you’re going to get a glass of switcher. You listed out steps to achieve that. With the declarative way you are saying exactly what you want to do.

Code Sample #1

function triple(arr) {

let results = [];

for(let i = 0; i < arr.length; i++) {

results.push(arr[i] * 3);


return results



By Looking at this example we can quickly notice that this is an imperative paradigm. The most obvious point is that this code sample is describing how to do something. We’re laying out steps explicitly explaining how we want to implement the functionality.

Code Sample #2

function triple(arr) {

return arr.map((item => item * 3);


In this code example, we are describing what we want instead of how. By using JavaScript’s built-in map method, we are not mutating any state. This code is more readable as well. We can see what is going on by first glance.

Tying this back to React. We know that when it comes to React, declarative programming finds its perfect home. React promotes a declarative approach to building user interfaces. React also introduces the virtual representation of the DOM, which acts as an abstraction layer. Simply tell React what you want the DOM to look like and you let React take control from there.

Declarative Programming in React empowers developers to focus on the "what" rather than the "how" of user interface (UI) development. It embraces its declarative nature by breaking down UI into reusable components and describing how they should behave based on the state. By leveraging React's virtual DOM with declarative programming, you'll harness the full power of React and create elegant and efficient user interfaces!

Advantages of Declarative programming in React:

  • Readability: Declarative code in React is more expressive and easier to understand, as it focuses on describing what the UI should look like rather than the specific update steps.

  • Performance Optimization: React's reconciliation algorithm, along with the virtual DOM, helps make updating the UI faster and smoother. It compares the previous version of the UI with the new one and figures out the exact changes that need to be made.

  • Maintainability: Declarative code makes it easier to reason about the UI's behavior, reducing bugs and making maintenance and updates smoother over time.

  • Reusability: Declarative components in React can be reused in different parts of the application, enabling modular development and reducing code duplication.

  • Testability: Declarative code is often more testable, as it focuses on inputs and expected outputs. React's component-based structure allows for easier unit testing.

In conclusion, We’ve learned the difference between declarative programming and imperative programming. We also now understand why React and declarative programming form a powerful combination. The combination revolutionizes the way we build user interfaces. This approach simplifies development, improves code maintainability, and enhances collaboration among team members.

Ultimately, declarative programming in React promotes a clearer and more intuitive codebase, making it easier to reason about and debug applications.