Declarative vs Imperative Programming

Imperative programming is a way of describing how things work. It explicitly specifies each statement, mutating a program’s state.

Declarative programming expresses the logic without explicitly specifying its control flow. It is a way of describing what you want to do, without listing all the steps to make it work.

• simple, easier to read, elegant code
• requires less effort to be understood
• no need to use variables
• avoids creating and mutating the state

Let's check if a number's a palindrome the imperative way:

function isPalindrome(word) {
    const len = word.length;
    for (let i = 0; i < len / 2; i++) {
        if (word[i] !== word[len - 1 - i]) {
            return false;
        }
    }
    return true;
}

A declarative solution would be:

function isPalindrome(word) {
    return word == word.split('').reverse().join('')
}