callback-functions.js

// Global Execution Context


logger(2); // on global stack, logs (2,3,1) runs inside function first because it was called before function. 
console.log(1)

function logger() {
    console.log(2)
    finish()
    console.log(3)
    function finish() {
        console.log("finished")
    }
}
logger(2); // runs after (1) in global stack logs (1,2,3)
// Function Execution Context


// What's a call back?

function message() {
    console.log("hello there")
}

// this is a higher order function, which means a function that takes another function as a param
function logger1(message) {
    message()
}

logger1(message)


// Other Examples of Callback Functions
// when you declare a function you can specify any argument that function can accept

function doSomething(value) {
    console.log("convert txt to uppercase" + " " + value.toUpperCase())
}
doSomething("robert") // string argument

function doSomething1(value) {
    console.log("math calcutation 10 * 20 = " + " " + value * 10)
}
doSomething1(20) // number

function doSomething2(value) {
    console.log("callback with .length function =" + " " + value.length)
}
doSomething2([1,2,3,4,5]) // array

// Different types of values can be passed through a function and as well as a function passed as an argument. 

// Pass the function as an arugment

// A callback function is a function that is passed as an argument to another function. 
// Using a callback functions allows you to call a function from another function. 

function doSomething3(value) {
    value()
}

// passing function as argument
doSomething3(function() {
    console.log("Sup G!")
})

// another example

function log(value) {
    console.log(value) // just logs the value that is passed to it. 
}

function calculateSum(num1, num2, print) {
    const sum = num1 + num2

    print(sum)
}

calculateSum(10,20, log)