Builder pattern example ported to TypeScript. See https://rafalstepien.com/zbyt-duza-liczba-parametrow-konstruktorze-wzorzec-projektowy-budowniczy-builder/

builder-pattern-typescript.ts

enum PokemonType {
    Water,
    Rock,
    Fire,
    Air,
    Electric,
    Poison
}

class Pokemon {
    private name?: string;
    private color?: string;
    private age?: number;
    private type?: PokemonType;
    private level?: number;

    constructor(builder: Pokemon.Builder) {
        this.name = builder.name;
        this.color = builder.color;
        this.age = builder.age;
        this.type = builder.type;
        this.level = builder.level;
    }
}

namespace Pokemon {
    /**
     * To do: merge namespace with Pokemon.
     * To do: spread arguments in constructor.
     * To do: optionality.
     */
    export class Builder {
        public name?: string;
        public color?: string;
        public age?: number;
        public type?: PokemonType;
        public level?: number;

        public withName(name: string) {
            this.name = name;
            return this;
        }

        public withColor(color: string) {
            this.color = color;
            return this;
        }

        public withAge(age: number) {
            this.age = age;
            return this;
        }

        public hasType(type: PokemonType) {
            this.type = type;
            return this;
        }

        public onLevel(level: number) {
            this.level = level;
            return this;
        }

        public build() {
            return new Pokemon(this);
        }
    }
}

const pikachu: Pokemon = new Pokemon.Builder()
                            .withName('Bob')
                            .withColor('yellow')
                            .withAge(13)
                            .hasType(PokemonType.Electric)
                            .onLevel(15)
                            .build();

See the improved version: https://gist.github.com/karol-majewski/1d2aee6b25892c7285555fda31327ba8