JS Interview Questions

Make great software and the tooling and learning will come.  

// Event Delegation

An event listener is fired on all child elements (event bubbling)
An event listener is fired on all parent elements (bubble up)

Target is what was actually clicked
Current Target is what the event listener is attached to
///////////////////////////////////////////////////////////

//IIFE - Immediately invoked function expression - write it and run it

variables inside an iffe are not available outside it.
(function taco() { }) ();
///////////////////////////////////////////////////////////

//Hoisting

when you use 'var' variables are acutally decalred first
when you write functions as statements they are hoisted too.

function statement() {};
function expression = () => {}

const and let are NOT hoisted -- scoped to block

///////////////////////////////////////////////////////////

//Undeclared

you forgot something somewhere
never declared a variable

//Undefined

declaration made by but contains nothing
empty array — let a = [];
index of an array  a[3]
variable declaration and then calling a property on it — a.name

const variable have to have a value upon declaration

//null

nothing value
not empty or zero

//Checking for undeclared, undefined, null

Undeclared finds you, except when assigning a value
Undefined  check with — taco === undefined (not a string)
Null -  taco === null
/////////////////////////////////////////////////////////////////////////////

//== - equality
=== - equality and type