veloii/def-gen

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

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