is-callable

What is is-callable?

The is-callable npm package is used to determine if a value is callable, meaning it can be called as a function. This is useful for type-checking in JavaScript where the typeof operator can be insufficient for certain cases, such as distinguishing between callable and non-callable objects.

What are is-callable's main functionalities?

Check if a value is callable

This feature allows you to check if various types of values are callable, including regular functions, async functions, arrow functions, and classes. It also correctly identifies non-callable objects like regex literals and plain objects.

const isCallable = require('is-callable');

console.log(isCallable(function() {})); // true
console.log(isCallable(async function() {})); // true
console.log(isCallable(() => {})); // true
console.log(isCallable(class MyClass {})); // true
console.log(isCallable(/regex/)); // false
console.log(isCallable(null)); // false
console.log(isCallable({})); // false

Other packages similar to is-callable

is-function

The is-function package is similar to is-callable in that it checks if a given value is a function. However, it may not handle all the cases that is-callable does, such as ES6 classes or callable objects.

lodash.isfunction

Lodash provides a method called isFunction which is part of the larger lodash utility library. It is similar to is-callable but is part of a larger set of utility functions and may not distinguish between all types of callable entities as is-callable does.

README

is-callable

Is this JS value callable? Works with Functions and GeneratorFunctions, despite ES6 @@toStringTag.

Example

var isCallable = require('is-callable');
var assert = require('assert');

assert.notOk(isCallable(undefined));
assert.notOk(isCallable(null));
assert.notOk(isCallable(false));
assert.notOk(isCallable(true));
assert.notOk(isCallable([]));
assert.notOk(isCallable({}));
assert.notOk(isCallable(/a/g));
assert.notOk(isCallable(new RegExp('a', 'g')));
assert.notOk(isCallable(new Date()));
assert.notOk(isCallable(42));
assert.notOk(isCallable(NaN));
assert.notOk(isCallable(Infinity));
assert.notOk(isCallable(new Number(42)));
assert.notOk(isCallable('foo'));
assert.notOk(isCallable(Object('foo')));

assert.ok(isCallable(function () {}));
assert.ok(isCallable(function* () {}));
assert.ok(isCallable(x => x * x));

Tests

Simply clone the repo, npm install, and run npm test