Type Safe Builder Pattern

A lightweight, zero-dependency TypeScript implementation of the Builder Design Pattern. This package ensures total type safety by preventing you from calling .build() until all required properties of your schema are defined.

✨ Key Features

- 🔒 Type Completion Enforcement: The .build() method is hidden via TypeScript's type system until every required property is set.
- 🧊 Immutable by Design: Every .set() call returns a new instance of the builder, allowing for easy branching and state sharing without side effects.
- 🛠️ Complex Type Support: Seamlessly handles Optionals, Unions, Enums, Nested Objects, Arrays, and Template Literals.
- 🚀 Bun Optimized: Developed and tested using the Bun runtime for maximum performance.

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📦 Installation

``bash


Using npm

`

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🚀 Quick Start

The core power of this library is that it makes "incomplete" objects impossible to build.

`typescript
import { objectBuilder } from "type-safe-builder-pattern";

type User = {
id: number;
username: string;
email: string;
isAdmin?: boolean; // Optional
};

const builder = objectBuilder()
.set("id", 1)
.set("username", "romeosarkar");

// ERROR: .build() does not exist yet because 'email' is missing!
// builder.build();

const user = builder.set("email", "romeo@example.com").build(); // Now it works!

console.log(user);
// { id: 1, username: "romeosarkar", email: "romeo@example.com" }
`

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💡 Advanced Usage

$3

Since each .set() returns a new instance, you can create a base configuration and branch off it.

`typescript
const baseConfig = objectBuilder()
.set("host", "localhost")
.set("port", 5432);

const devConfig = baseConfig.set("database", "dev_db").build();
const prodConfig = baseConfig.set("database", "prod_db").build();
`

$3

The builder maintains full type safety for complex nested structures.

`typescript
type Project = {
name: string;
tags: string[];
metadata: {
version: string;
};
};

const myProject = objectBuilder()
.set("name", "TypeSafeApp")
.set("tags", ["typescript", "builder"])
.set("metadata", { version: "1.0.0" })
.build();
`

---

🛠️ Development

This project uses Bun for development and testing.

$3

- Bun >= 1.x
- Node.js >= 25 (for runtime compatibility)

$3

`bash


Install dependencies

`

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📄 License

MIT © Romeo Sarkar

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$3

In large-scale applications, creating complex objects with many required fields can become messy. Using this builder:

1. Prevents Runtime Errors: You can't accidentally forget a field.
2. Improves Readability: Named .set(key, value)` calls are often clearer than large object literals.
3. Encourages Immutability: Easier to maintain state in functional environments.