Imperative Programming
* Focuses on "How": Tells the computer *how* to do something, step by step.
* Think in terms of instructions: It involves a sequence of commands that modify the program's state directly.
* Like a recipe: You specify the exact ingredients and order of steps.
* Example:
```
let x = 5;
x = x + 10;
console.log(x); // Outputs 15
```
Here, you explicitly tell the computer to create a variable `x`, assign it a value, then increment it, and finally display it.
Declarative Programming
* Focuses on "What": Describes *what* you want the computer to achieve, not *how* to do it.
* Think in terms of data and relationships: It defines the desired outcome or result without specifying the steps.
* Like a blueprint: You define the desired structure and properties, but not the exact construction process.
* Example:
```javascript
const nums = [1, 2, 3, 4, 5];
const sum = nums.reduce((acc, cur) => acc + cur, 0);
console.log(sum); // Outputs 15
```
Here, you don't explicitly loop through the array and add numbers. You use the `reduce` method, which handles the iteration and addition internally based on the provided logic.
Key Differences in a Nutshell:
| Feature | Imperative | Declarative |
|----------------|--------------------------------------------|--------------------------------------------|
| Focus | How to accomplish a task | What to achieve |
| Code Structure | Sequence of commands, state manipulation | Data transformations, logical expressions |
| Examples | C, Java, Python (for procedural code) | SQL, HTML, CSS, Functional Programming |
Choosing Between Paradigms:
* Imperative: Useful for low-level control and optimization, good for understanding how things work.
* Declarative: Leads to more concise and readable code, better for complex data manipulation and higher-level abstractions.
In Practice:
Many programming languages are not purely imperative or declarative. They often support both styles. For instance, Python can be used in both imperative and functional (declarative) ways. The choice depends on the specific problem you're trying to solve and the desired level of abstraction.