Functions and Methods in Java

What is a function?

A function is a block of code designed to perform a particular task, this task is executed when invoked:

const greetings = function(){
console.log('Hello User');
};
greetings();

What is a Method?

A method is quite similar to a function, however the way they are invoked and defined differ:

const welcome = `Welcome ${userName}`
let userName = 'Daniel';
let welcomeAlert = welcome.toUpperCase();
//* the line of code above uses a method called toUpperCase *//
console.log(welcomeAlert);

What is an argument?

Function parameters are the names listed in the function definition. Function arguments are the real values passed to the function:

const speak = function(name = 'Daniel', time = 'night'){
//* the parameters are the variables "name" and "time" *//
console.log(`Good ${time} ${name} ); }
speak('Alejandro', 'morning')
//* the code above is the argument that alters the function's result *//

How to return a value:

const calcArea = function(radius){
let area = 3.14 * radius**2;
return area;
}
console.log(area);
//* This function will log the results into the console *//

Arrow Functions

Arrow functions allow us to write shorter function syntax. If the function has only one statement, and the statement returns a value, you can remove the brackets and the return keyword. This only works if the functions has one statement.

const calcArea = (radius) = {
    return 3.14 * radius**2;
}
//* This function is the same as the one above, it is more compact *//

What is the Foreach Method?

This method calls a function once for each element in an array, in order:

let group = ['Carolina', 'Daniel', 'Piper']
const logGroup= (group, index) => {
console.log(`${index} - hello ${group}`);
group.forEach(logGroup);

Callback Functions

A callback is a function passed as an argument to another function:

function myAlarm(){
console.log('Wake UP!')};
function warning(){
console.log('You've got 10 minutes left!')};
warning();
myAlarm();

Resources

www.w3schools.com

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