JS Aside: First-Class Functions and function expressions

Big Word

First-Class functions: Everything you can do with other types you can do with functions.

You can use functions like strings, numbers, etc. (i.e. pass them around, set variables equal to them, put theme in arrays, and more)

An expression: A block of code that results in a value

Function expressions are possible in javascript because functions are first-class.

Invoke: run the function

We can also say 'call' the function

The code

// function statement

// this is a function statement, when creating excuetion context, it will be sitting in memery and be ariablve to you,
// you can invoke this function even before the function definition
function greet() {
    console.log('hi');
}
greet();

// functions are first-class
// meaning you can pass function around as pamameters
function logGreeting(fn) {
    fn();
}
logGreeting(greet);

// function expression
// this is intresting, it will get hositing when excuetion context creation phrace, meaning you get undefined
// when code did not reach this line
var greetMe = function() {
    console.log('Hi Tony!');
}
greetMe();

// it's first-class
// pass a varible to it, the varibla points to a function
logGreeting(greetMe);

// use a function expression to create a function on the fly
// you can't do this in other programing langugaes, which why js is so cool
logGreeting(function() {
    console.log('Hello Tony!');
});