javascript - type comparison functions to cleanup code

typechecks.js

const isFn = (a) => typeof a === 'function';
const isString = (a) => typeof a === 'string';
const isNumber = (a) => typeof a === 'number';

const isArray = Array.isArray;
const isObject = (a) => a !== null && typeof a === 'object';
const isActualObject = (a) => isObject(a) && !isArray(a);