TS builder pattern

TS strict builder class

interface SomeInterface {
  a: string
  b: number
  c: boolean
}

export class Builder<T extends Partial<SomeInterface>> {
  readonly #current: T

  static create<T extends Partial<SomeInterface>>(init: T) {
    return new Builder({ ...init })
  }

  constructor(init: T) {
    this.#current = init
  }

  setA(value: string) {
    return new Builder({ ...this.#current, a: value })
  }

  setB(value: number) {
    return new Builder({ ...this.#current, b: value })
  }

  setC(value: boolean) {
    return new Builder({ ...this.#current, c: value })
  }

  build(this: Builder<SomeInterface>): SomeInterface {
    return {
      a: this.#current.a,
      b: this.#current.b,
      c: this.#current.c
    }
  }
}

const typedObject = Builder.create({ a: 'a' }).setB(666).setC(true).build()