How do I create a function factory in JavaScript?

How do I create a function factory in JavaScript?

A function factory is a function that returns other functions. You can create one like this:

function makeCounter() {
    let count = 0;
    return function() {
        count++;
        return count;
    };
}
const counter = makeCounter();
console.log(counter()); // 1
console.log(counter()); // 2

This makeCounter function returns a new function that increments and returns the count each time it's called.

Can you explain how closures work in this example?

Sure! In this example, the inner function has access to the count variable defined in the outer makeCounter function. This is due to closures, which allow the inner function to 'remember' the environment in which it was created, even after the outer function has finished executing.

What are some practical uses for function factories?

Function factories can be used for creating customizable functions, like event handlers, or for managing state in applications. They help in encapsulating logic and maintaining private variables.

Can you show me another example of a function factory?

Absolutely! Here's another example that creates a multiplier function:

function makeMultiplier(factor) {
    return function(x) {
        return x * factor;
    };
}
const double = makeMultiplier(2);
console.log(double(5)); // 10

This makeMultiplier function returns a new function that multiplies its input by the specified factor.