The Difference Between Declarative and Imperative Programming

Programming allows us to solve a particular problem in various ways. We are free to choose any approaches available or can even follow our own custom approach.

However, there are some popular programming styles which every programmer should learn in their career. Today, I will talk about declarative and imperative programming and the difference between them.

Read: What’s the Difference Between Coding and Programming?

Contents

What is Declarative Programming?

Starting with declarative programming, it’s a style of programming where the programmer is most concerned about the result or what a program should return. They don’t bother about writing the best performing code or follow any particular path, they just focus on getting the expected answers.

const sum = a => b => a + b; 

console.log (sum (5) (3)); // 8

What is Imperative Programming?

Next, let’s talk about imperative programming. It’s a style of programming where a programmer cares about how to reach a particular result, step by step. Here, the programmer also wants the same result ultimately, but he/she tell the compiler to do things in a certain way to get the expected result.

class Number {
constructor (number = 0) {
this.number = number;
}
add (x) {
this.number = this.number + x;
}
}
const myNumber = new Number (5);
myNumber.add (3);
console.log (myNumber.number); // 8

If you are still confused about both of these programming forms, let’s understand it with an example. Suppose, you want to outsource work but also know you need this skill for the long term, and you’re confused between outsourcing work or learn a skill.

Now, you can compare this situation with the declarative and imperative programming approaches. If you outsource work, you might not care about the way work is completed. You just care about the final product or result. This is like declarative programming where you know the final result and write a program to achieve that.

On the other hand, if you decide that you want to learn this skill for the long term, you may now attempt to complete the task caring about how it is actually done. You need to understand the individual steps required to get it working properly. This is similar to imperative programming.

Also Read: Difference Between Frameworks and Libraries in Computer Science

Which One You Should Follow in Your Projects?

There are advantages and disadvantages to both the programming approaches. It entirely depends on you, the programmer, which implementation you would like to follow in your code. Let’s have a look at the following properties which can help take the right decision.

Reusability

Declarative programming allows you to write more general functions that could potentially be used for multiple purposes. This promotes faster development and also make the functionality available for others. On the other hand, in imperative programming, your code may be applicable for only that particular project or application.

Chances of Error

Declarative programming requires you to write functions that do not change their state as they do in functional programming. This decreases the chances of errors and makes your application more stable. The removal of side effects from your functions helps you to understand exactly what comes in and what comes out, and thus make the program more predictable.

Control

In order to achieve desired results, using ready-made functions is common in declarative programming. However, you may also need specific changes in the function to make it provide the desired results. But you usually don’t have this control in declarative programming as you would have in imperative programming.

Conclusion

I hope this article helped you understand the differences between declarative and imperative programming. If you care about the implementation, go with an imperative approach. Otherwise, the declarative style works beautifully for many developers. Also, you can even mix both styles. It’s extremely flexible and after all, you are in charge.