Javascript for in and for of

Day 4: for in and for of loops

In short, Iterates over statements which are true.


The differences between for of and for in are illustrated below. However, I still can’t wrap my head around it.

Object.prototype.objCustom = function() {};
Array.prototype.arrCustom = function() {};
let iterable = [3, 5, 7]; = 'hello';
for (let i in iterable) {
console.log(i); // logs 0, 1, 2, "foo", "arrCustom", "objCustom"
for (let i of iterable) {
console.log(i); // logs 3, 5, 7

Coercion in Javascript

Mallet smshing an egg

Day 3: Coercion

To oversimplify this is the act of converting a value from one type to another. An array to a number, a string to an boolean etc.

var a = 42;
var b = a + ""; // implicit coercion
var c = String( a ); // explicit coercion

You Don’t Know JS

Javascript Loop

Day Two – Loops

Took a look at the for and for / in loops and how they’re used in variables and objects to pull information.

var warGoodForObject = {
"what": "nothing",
"who": "no one"
for( var name in warGoodForObject ) {
console.log ( name + ": " + warGoodForObject[name] );

Results in console:
what: nothing
who: no one

100 Days of Javascript

Javascript For Web Designers by Mat Marquis

Starting today I’m taking on the challenge to re-learn javascript. The last ten years have led to countless updates, APIs and new frameworks that I’ve largely ignored in favor of focusing on HTML, CSS and enough PHP to get the job done in WordPress.

Day One: Relearning the basics

Javacript for Web Designers by Mat Marquis

Specifically chapter three which focuses on conditional statements such as if, else and else if. True and false and math.

I expect the first 30 days will find me reading about the DOM and running tests in my browser’s console before the actual fun begins.