JS Variable Keywords

`const`, `let`, `var`

Variables provide developers a way to store a value
Once a variable is declared, the name of the variable is called an identifier
For example, const name = 'kim'; `name is the identifier
In JavaScript, variable identifiers can contain the letters (a-z), numbers (0-9), underscores (_) and the dollar sign ($)

const

Used when the value of the variable will stay the same
Throws an error if there is an attempt at updating the value
Block scope: can see/has access to only what is inside the curly braces. Can be a function, loop or conditional
Need to be declared and initialized at the same time because you cannot reassign a value
ALL_CAPS or lowercase? Application level constants yes, not when you use const for declaring immutable variables in function scope.
Use const as often as possible to minizimize mutable state

Example:

const API_URL = asdlkfjasldkfjasdf.com/v1/plants;

function filterData(){
    const result = {};
    // code here
    return resut;
}

let

Used when the value of the variable will be reassigned
Most commonly used in for loops
Block scope: can see/access what is inside the curly braces. can be a function, loop or conditional.

var

In ES5 and prior versions of ECMAScript, var was the only variable declaration keyword
Avoid var
When is var used in ES6?
function scope: can see/has access to anything within the curly braces of a function