More on the book. What i learnt today:

Closure:

being able to reference a specific instance of a local binding in an enclosing scope. A function that references bindings from local scopes around it is called a closure.

A pure function

a specific kind of value-producing function that not only has no side effects but also doesn’t rely on side effects from other code—for example, it doesn’t read global bindings whose value might change. A pure function has the pleasant property that, when called with the same arguments, it always produces the same value

Array Methods

includes() - checks if a given value exists in the array.
shift() - removes the first(zero index) item from an array.
unshift() - adds a item at the front(zero index) of an array
indexOf() - searches through the array from the start to the end and returns the index at which the requested value was found
lastIndexOf() - searches through the array from the end(last item)
trim () - removes whitespace (spaces, newlines, tabs, and similar characters) from the start and end of a string
... Spread Syntax - expands or spreads out an array, passing its elements as separate arguments.

Looping through arrays using let item of items.

for (let item of items) { 
console.log(item); 
}

Math Object functions

Math.floor() - rounds down
Math.ceil() - rounds up
Math.round() - rounds to the nearest whole number
Math.abs() - takes the absolute value of a number, Negates a negative.

What is JSON?

A serialization format. Serialization means converting to a a flat description.
Json Methods
JSON. parse() Converts a JSON string to a JavaScript object
JSON. stringify() Converts a JavaScript object to a JSON string

That's it for Day 80
I'll continue with the book tommorrow