JavaScript Interview EP

js-testing.js

/**
 * @param {Object} obj
 * @returns {string}
 */
function getFirstKey(obj) {
    return Object.keys(obj)[0];
}

/**
 * @type {Object}
 */
const container = {};

/**
 * @type {string}
 */
const containerId = 'widgetContainer';

// JS define variable keywords

// when to use let vs const

// const
// what is the scope behavior for const
// when is the const available for use when defined beneath where it is being accessed
// 
// what happens when a const is not set a a value
// const is set to undefined and then set again
// const is set to a value and then set to another value
// const is set to a reference and then set again to the same reference
// const is set to a reference and then set again to a new reference

// let
// what is the scope behavior for let

// var
// what happens when a var is used when the js file has the "use strict defined at the top of the file"

// what happens when a variable is set to a value when it has not been defined
// is there any difference when the js file is not in strict mode?
// what happens when a variable is set to a value when is has already been defined


// JS Types related to numbers (int,float,NaN,-1)
const numExZero = 0;

const numExInteger = 1;

const numExFloatingPointRound = 1.0;

const numExFloatingPointDecimal = 1.1;

const numExFloatingPointRoundNegative = -1.1;

const numExFloatingPointDecimalNegative = -1.1;

const numExNotANumber = NaN;

const numExZeroDividedByZero = 0/0;


// event loop
// how to skip to the next js execution loop
// setInterval, setTimeout (when to use the timer vs the render event)
// add event listener for the render event (what happens to the scope in the render event)
// what happens when the js event loop has code that takes longer? (IE if 60fps/30fps)
// what ways cant he event loop be debugged in the developer tools

// Iframes 
// what happens when an IFrame is from a domain that is external to the parent domain
// when the IFrame is from a subdomain
// how is the nested iframe able to pass data to the parent 
// how is the nested iframe able to access dom elements from the parent

// Document
// what happens when document write is called multiple times
// and when document write is called multiple times but with a time delta between each call
// what happens when document write is called from within an iframe

// Arrays
// mutating vs copying 
const arr = [];
// copy an array
// mutate an array
// combine arrays
// combine part of one array with part of another array

// iterating arrays
// using for
// using while
// using Array.forEach

// what are the different scenarios that you would want to use each of the different types
// what are the differences in performance between each of the methods? (chrome, safari, ff)

// regex
// what are the basic usages of regex
// how to define a regex literal
// how to define a custom regex
// what are the performance concerns using the new RegEx constructor, how can it be mitigated

// code security
// code defined dynamically
// what are the ways that js can be constructed dynamically
// cross domain security, what can be done on the front end vs the server

// how to be defensive with user input


// context senarios

// promises usage

// generator usage