JavaScript Cheatsheet

Contains handy info

Array methods

Array methods categories

Test if a variable is an Array

const arr = [1,2,3]

// Method 1

Array.isArray(arr) // true

// Method 2

console.log(arr instanceof Array) // true // but also note  - 
// arr instanceof Object  is also true, so you can do this below

if(Array.isArray(arr) && arr instanceof Array) // actually Array.isArray is sufficient

Test if a variable is an Object

// This is tricky because array is an object, function is an object so it's difficult
// to find the actual object

// Problem
const arr = []
const fun = function(){}
const actualObj = {}

arr instanceof Object // true
fun instanceof Object // true
actualObj instanceof Object // true


// So the goal is actualObj must return true and everything else false
actualObj instanceof Object && !(actualObj instanceof Array) && !(typeof actualObj === 'function')

Check if a value is an object in JavaScriptStack Overflow