def-gen

A powerful tool to infer types from JavaScript values and generate code from these inferred types.

[!NOTE]
More generators, including Zod and Valibot, will be coming soon.

Installation

Install Locally

To install the package locally in your project, run:

npm install def-gen

Install Globally

To install the package globally so you can use the CLI, run:

npm install -g def-gen

Quick Start Guide

Step 1: Import the Required Functions and Classes

Import the inferValue, inferValues, and TypeScriptGenerator from the package.

import { inferValue, inferValues, TypeScriptGenerator } from 'def-gen';

Step 2: Create a Code Generator

Create an instance of the TypeScriptGenerator with your desired configuration.

const generator = new TypeScriptGenerator({
  indentationSpaces: 2,
  exportType: true,
  typeName: "MyType"
});

Step 3: Infer Types and Generate Code

Use inferValue or inferValues to infer types from your JavaScript data and generate the corresponding code.

Example with a Single Value

const jsValue = {
  name: "Alice",
  age: 30
};

const output = inferValue(jsValue, {
  generator: generator,
  literalKeys: ["name"]
});

console.log(output);
// Output:
// export type MyType = {
//   name: "Alice";
//   age: number;
// }

Example with Multiple Values

const jsValues = [
  { name: "Alice", age: 30 },
  { name: "Bob", age: 25 }
];

const output = inferValues(jsValues, {
  generator: generator,
  literalKeys: ["name"]
});

console.log(output);
// Output:
// export type MyType = {
//   name: "Alice" | "Bob";
//   age: number;
// }

CLI Usage

If you have installed def-gen globally, you can use the CLI to generate types from a JSON file.

def-gen [flags...] <json file path>

Flags

• -e, --export: Export any declarations or variables outputted.
• -g, --generator <value>: Type of format to be output (ts) (default: "ts").
• -h, --help: Show help.
• -i, --indentation <number>: Amount of spaces used for indentation (default: 2).
• -l, --literal-keys <string>: Dot separated keys (object.key) to be interpreted as a literal (default: []).
• -n, --name <string>: Name used for the final variable or type.

Example

def-gen -e -g ts -i 4 -l "user.name" -n "UserType" path/to/data.json

API Documentation

inferValue

Infers the type of a single value and generates code using the specified generator.

Parameters:

• value: unknown: The value to infer the type from.
• config: Config: The configuration for type inference and code generation.

Returns:

• string: The generated code.

inferValues

Infers the types of multiple values and generates code using the specified generator.

Parameters:

• values: unknown[]: The values to infer the types from.
• config: Config: The configuration for type inference and code generation.

Returns:

• string: The generated code.

TypeScriptGenerator

A class for generating TypeScript code from inferred types.

Constructor:

• config?: TypeScriptGeneratorConfig: Optional configuration for the TypeScript generator.
  • indentationSpaces?: number: Number of spaces to use for indentation (default: 2).
  • typeName?: string: The name of the generated type.
  • exportType?: boolean: Whether to export the generated type (default: false).

Configuration Types

Config

Configuration for type inference and code generation.

• literalKeys?: string[]: An array of dot-separated keys that will be turned into literal values.
• generator: CodeGenerator: The code generator to use for generating code from inferred types.

TypeScriptGeneratorConfig

Configuration for the TypeScript code generator.

• indentationSpaces?: number: Number of spaces to use for indentation (default: 2).
• typeName?: string: The name of the generated type.
• exportType?: boolean: Whether to export the generated type (default: false).

License

MIT