lodash.isfunction

The Lodash method _.isFunction exported as a standalone module for checking if a value is classified as a Function object. This utility provides robust function detection that handles modern JavaScript function types including regular functions, async functions, generator functions, and proxy-wrapped functions while properly handling edge cases and cross-environment compatibility.

Package Information

• Package Name: lodash.isfunction
• Package Type: npm
• Language: JavaScript
• Installation: npm install lodash.isfunction

Core Imports

CommonJS (primary):

const isFunction = require("lodash.isfunction");

ESM (via interop):

import isFunction from "lodash.isfunction";

TypeScript:

import isFunction from "lodash.isfunction";
// Note: No built-in TypeScript definitions. Function returns boolean.

Basic Usage

const isFunction = require("lodash.isfunction");

// Regular functions
isFunction(function() {});           // => true
isFunction(() => {});                // => true

// Async functions
isFunction(async function() {});     // => true
isFunction(async () => {});          // => true

// Generator functions
isFunction(function* () {});         // => true

// Built-in functions
isFunction(Array.prototype.slice);   // => true
isFunction(console.log);             // => true

// Non-functions
isFunction(/abc/);                   // => false
isFunction({});                      // => false
isFunction("function");              // => false
isFunction(null);                    // => false
isFunction(undefined);               // => false

Capabilities

Function Detection

Checks if a value is classified as a Function object using robust type detection that works across different JavaScript environments.

/**
 * Checks if `value` is classified as a `Function` object.
 *
 * @param {*} value The value to check.
 * @returns {boolean} Returns `true` if `value` is a function, else `false`.
 * @since 0.1.0
 * @category Lang
 * @example
 *
 * const isFunction = require('lodash.isfunction');
 * 
 * isFunction(function() {});
 * // => true
 *
 * isFunction(/abc/);
 * // => false
 */
function isFunction(value: any): boolean;

Function Types Detected:

• Regular functions (function() {})
• Arrow functions (() => {})
• Async functions (async function() {}, async () => {})
• Generator functions (function* () {})
• Proxy-wrapped functions
• Built-in functions (Array.prototype.slice, console.log, etc.)

Implementation Details:

• Uses Object.prototype.toString for reliable type detection
• Handles Symbol.toStringTag for custom objects
• Avoids Safari 9 issues with typeof operator on typed arrays
• Works consistently across different JavaScript environments

Browser Compatibility:

• Works in all modern browsers
• Compatible with Node.js environments
• Handles cross-frame scenarios properly