deca-method-lister/index.js

A utility to extract and list all methods from JavaScript objects, including inherited methods from the prototype chain

/**
 * Extracts and returns all method names from a JavaScript object, including inherited methods from the prototype chain.
 * 
 * This 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).
 * 
 * @param {Object} obj - The object to extract methods from
 * @returns {string[]} An array of method names (strings) available on the object
 * 
 * @example
 * // Simple object with custom methods
 * const myObject = {
 *   name: 'John',
 *   greet() { return `Hello, I'm ${this.name}`; },
 *   getInfo() { return this.name; }
 * };
 * 
 * const methods = getMethods(myObject);
 * console.log(methods); // ['greet', 'getInfo', 'constructor', 'hasOwnProperty', 'toString', ...]
 * 
 * @example
 * // Built-in JavaScript objects
 * const arr = [];
 * const arrayMethods = getMethods(arr);
 * console.log(arrayMethods); // ['push', 'pop', 'slice', 'splice', 'map', 'filter', ...]
 */
const getMethods = (obj) => {
    let properties = new Set()
    let currentObj = obj
    do {
      Object.getOwnPropertyNames(currentObj).map(item => properties.add(item))
    } while ((currentObj = Object.getPrototypeOf(currentObj)))
    return [...properties.keys()].filter(item => typeof obj[item] === 'function')
}

module.exports = {
    getMethods
}