functionsIn (Lodash compatibility)

Use for...in loop and typeof check instead

This functionsIn function operates slowly due to the for...in loop and function checking process.

Instead, use the faster and more modern for...in loop and typeof check.

Returns an array of the names of all properties (including inherited properties) of an object that are functions.

const functionNames = functionsIn(obj);

Reference

functionsIn(object)

Checks all properties of an object and returns an array of only the names of properties that are functions. It checks not only the object's own properties but also all properties inherited through the prototype chain. This is useful for finding all methods (including inherited methods) of an object.

import { functionsIn } from 'es-toolkit/compat';

// Basic usage
const obj = {
  name: 'John',
  age: 30,
  greet: () => 'Hello',
  calculate: function (x, y) {
    return x + y;
  },
};

const functionNames = functionsIn(obj);
// Result: ['greet', 'calculate']

// Including inherited functions
class Calculator {
  constructor() {
    this.value = 0;
    this.add = function (n) {
      this.value += n;
    };
  }

  multiply(n) {
    this.value *= n;
  }
}

Calculator.prototype.divide = function (n) {
  this.value /= n;
};

const calc = new Calculator();
const allMethods = functionsIn(calc);
// Result: ['add', 'divide'] (`multiply` is non-enumerable)

// Inheritance through prototype chain
function Parent() {
  this.parentMethod = function () {
    return 'parent';
  };
}
Parent.prototype.protoMethod = function () {
  return 'proto';
};

function Child() {
  Parent.call(this);
  this.childMethod = function () {
    return 'child';
  };
}
Child.prototype = Object.create(Parent.prototype);

const child = new Child();
const inheritedFunctions = functionsIn(child);
// Result: ['parentMethod', 'childMethod', 'protoMethod']

null or undefined are treated as empty arrays.

import { functionsIn } from 'es-toolkit/compat';

functionsIn(null); // []
functionsIn(undefined); // []

Parameters

• object (any): The object to inspect.

Returns

(string[]): Returns an array of the names of properties that are functions (including inherited functions).