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];
iterable.foo = '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