deca-method-lister

A lightweight utility to extract and list all methods from JavaScript objects, including inherited methods from the prototype chain. Now with CLI support for analyzing JavaScript files!

Installation

npm install deca-method-lister

Usage

Programmatic Usage

const { getMethods } = require('deca-method-lister');

// Example with a simple object
const myObject = {
  name: 'John',
  age: 30,
  greet() {
    return `Hello, I'm ${this.name}`;
  },
  getAge() {
    return this.age;
  }
};

const methods = getMethods(myObject);
console.log(methods);
// Output: ['greet', 'getAge', 'constructor', 'hasOwnProperty', 'isPrototypeOf', 'propertyIsEnumerable', 'toString', 'valueOf', 'toLocaleString']

CLI Usage

Analyze JavaScript files and generate method documentation:

# Analyze a JavaScript file
npx deca-method-lister myfile.js

# Specify output file (default: methods.js)
npx deca-method-lister myfile.js output.js

Example CLI Output:

$ npx deca-method-lister index.js
✅ Successfully analyzed index.js
📄 Found 1 methods
💾 Generated methods.js

📋 Methods found:
1. getMethods (line 27)
   └─ Extracts and returns all method names from a JavaScript object, including inherited methods from the prototype chain.

Generated File Structure:

// Auto-generated method information for index.js
// Generated on 2024-01-15T10:30:00.000Z

const methods = [
  {
    "name": "getMethods",
    "description": "Extracts and returns all method names from a JavaScript object, including inherited methods from the prototype chain.",
    "parameters": [
      {
        "type": "Object",
        "name": "obj",
        "description": "The object to extract methods from"
      }
    ],
    "returnType": "string[]",
    "file": "index.js",
    "line": 27
  }
];

module.exports = {
    methods,
    count: methods.length,
    file: 'index.js',
    generatedAt: '2024-01-15T10:30:00.000Z'
};

Examples

Built-in Objects

const { getMethods } = require('deca-method-lister');

// Array methods
const arr = [];
const arrayMethods = getMethods(arr);
console.log(arrayMethods);
// Output: ['push', 'pop', 'shift', 'unshift', 'slice', 'splice', 'concat', 'join', 'reverse', 'sort', 'filter', 'map', 'reduce', 'forEach', ...]

// String methods
const str = "hello";
const stringMethods = getMethods(str);
console.log(stringMethods);
// Output: ['charAt', 'charCodeAt', 'concat', 'indexOf', 'lastIndexOf', 'slice', 'substring', 'substr', 'toLowerCase', 'toUpperCase', ...]

// Date methods
const date = new Date();
const dateMethods = getMethods(date);
console.log(dateMethods);
// Output: ['getTime', 'getFullYear', 'getMonth', 'getDate', 'getHours', 'getMinutes', 'getSeconds', 'setTime', 'setFullYear', ...]

Custom Classes

const { getMethods } = require('deca-method-lister');

class Animal {
  constructor(name) {
    this.name = name;
  }
  
  speak() {
    return `${this.name} makes a sound`;
  }
  
  move() {
    return `${this.name} moves`;
  }
}

class Dog extends Animal {
  constructor(name, breed) {
    super(name);
    this.breed = breed;
  }
  
  bark() {
    return `${this.name} barks`;
  }
  
  fetch() {
    return `${this.name} fetches the ball`;
  }
}

const dog = new Dog('Buddy', 'Golden Retriever');
const dogMethods = getMethods(dog);
console.log(dogMethods);
// Output: ['bark', 'fetch', 'speak', 'move', 'constructor', 'hasOwnProperty', 'isPrototypeOf', ...]

Filtering Results

const { getMethods } = require('deca-method-lister');

const myObject = {
  customMethod1() { return 'one'; },
  customMethod2() { return 'two'; }
};

const allMethods = getMethods(myObject);
const customMethods = allMethods.filter(method => 
  !['constructor', 'hasOwnProperty', 'isPrototypeOf', 'propertyIsEnumerable', 'toString', 'valueOf', 'toLocaleString'].includes(method)
);

console.log(customMethods);
// Output: ['customMethod1', 'customMethod2']

API

getMethods(obj)

Returns an array of all method names (functions) available on the given object, including inherited methods from the prototype chain.

Parameters

• obj (Object): The object to extract methods from

Returns

• Array<string>: An array of method names

Example

const { getMethods } = require('deca-method-lister');

const methods = getMethods(someObject);
console.log(methods); // ['method1', 'method2', 'inheritedMethod', ...]

CLI Features

The CLI tool analyzes JavaScript files and extracts:

• Method names and their locations (line numbers)
• JSDoc documentation including descriptions, parameters, and return types
• Function signatures with parameter names
• Method metadata including file information and timestamps

Supported Method Patterns

• Function declarations: function methodName() {}
• Arrow functions: const methodName = () => {}
• Object method shorthand: methodName() {}
• Class methods: methodName() {}
• Async methods: async methodName() {}

JSDoc Support

The CLI automatically extracts JSDoc comments and parses:

• Method descriptions
• @param tags with types and descriptions
• @returns tags with return types
• Method parameters from function signatures

How it Works

The getMethods function traverses the entire prototype chain of the given object using Object.getPrototypeOf() and collects all property names using Object.getOwnPropertyNames(). It then filters the results to include only properties that are functions (methods).

This approach ensures that:

• All own methods are included
• All inherited methods from the prototype chain are included
• Only functions are returned (properties with other types are filtered out)
• Duplicate method names are automatically handled by using a Set

Use Cases

• API Documentation: Automatically generate documentation for object methods
• Code Analysis: Analyze JavaScript files to understand their structure
• Testing: Ensure all expected methods are available on objects
• Debugging: Quickly inspect what methods are available on an object
• Introspection: Build tools that need to understand object capabilities
• Educational: Learn about JavaScript's prototype chain and inheritance

License

MIT

Author

Tom Tarpey

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Repository

GitHub Repository