mock-builder

Overview

The mock-builder is a TypeScript library designed to help you create objects based on a specified shape. Each property in the shape can be either a static value or a function that returns a value. The library emphasizes immutability, ensuring that each modification creates a new instance, thereby avoiding side effects and promoting predictable, maintainable code.

Features

• Immutable Design: Ensures that every operation returns a new instance, avoiding unintended side effects.
• Flexible Shape Definition: Supports both static values and functions that generate values.
• TypeScript Support: Fully typed for a robust development experience.
• Chainable API: Easily chain methods for building complex objects.

Installation

Install the package via npm:

npm i -D @brunoss/mock-builder

Usage

Basic Usage

import { Builder } from 'immutable-builder';

// Define a shape for the object
const builder = new Builder({
  id: () => Math.floor(Math.random() * 100),
  name: 'defaultName'
});

// Build the object
const myObject = builder.build();

console.log(myObject);
// Output: { id: 42, name: 'defaultName' }

Applying Default Values

const builder = new Builder({
  id: 1,
  name: 'Alice'
});

// Apply default values
const updatedBuilder = builder.applyDefaultValues({
  age: () => 30, // Function executed during build
  isActive: true
});

const myObject = updatedBuilder.build();
console.log(myObject);
// Output: { id: 1, name: 'Alice', age: 30, isActive: true }

Setting Values Conditionally

const builder = new Builder({
  id: 1,
  name: 'Alice'
});

// Set values based on a condition
const updatedBuilder = builder.setConditionalValue(
  'isAdmin',
  userType === 'admin',
  true,
  false
);

const myObject = updatedBuilder.build();
console.log(myObject);
// Output: { id: 1, name: 'Alice', isAdmin: false }

API

Builder

constructor(shape: Shape<T>)

• Creates a new Builder instance.
• Parameters:
  • shape: An object where each key is a property of the resulting object and can be either a value or a function that returns a value.

build(): T

• Constructs an object based on the shape provided during instantiation.
• Returns: An object of type T with all values resolved.

withValue<K extends keyof T>(prop: K, value: T[K]): Builder<T>

• Sets a specific property of the shape to always return a given value.
• Parameters:
  • prop: The property name to set.
  • value: The value that the property should always return.
• Returns: A new Builder instance.

setConditionalValue<K extends keyof T>(prop: K, condition: boolean, trueValue: T[K], falseValue: T[K]): Builder<T>

• Sets a property based on a condition.
• Parameters:
  • prop: The property name to set.
  • condition: The condition to evaluate.
  • trueValue: The value if the condition is true.
  • falseValue: The value if the condition is false.
• Returns: A new Builder instance.

applyDefaultValues(defaults: Partial<Shape<T>>): Builder<T>

• Applies default values to undefined properties. If a default value is a function, it runs during build() to get the final value.
• Parameters:
• defaults: An object containing default values for properties.
• Returns: A new Builder instance.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request or open an Issue on GitHub.

Credits

based on fluentbuilder