Factory Functions

A factory function creates a configured object without exposing setup details to callers.

factory.ts

type Counter = {
    increment(): void;
    value(): number;
};

function createCounter(start: number): Counter {
    let current: number = start;
    return {
        increment(): void {
            current = current + 1;
        },
        value(): number {
            return current;
        },
    };
}

const startValue: number = ;
const counter: Counter = createCounter(startValue);

counter.increment();
counter.increment();

console.log(`value=${counter.value()}`);

type Counter = {
    increment(): void;
    value(): number;
};

function createCounter(start: number): Counter {
    let current: number = start;
    return {
        increment(): void {
            current = current + 1;
        },
        value(): number {
            return current;
        },
    };
}

const startValue: number = ;
const counter: Counter = createCounter(startValue);

counter.increment();
counter.increment();

console.log(`value=${counter.value()}`);

type Counter = {
    increment(): void;
    value(): number;
};

function createCounter(start: number): Counter {
    let current: number = start;
    return {
        increment(): void {
            current = current + 1;
        },
        value(): number {
            return current;
        },
    };
}

const startValue: number = ;
const counter: Counter = createCounter(startValue);

counter.increment();
counter.increment();

console.log(`value=${counter.value()}`);

factory function A factory function returns a new object that already has the data and methods it needs.