function.md

Functions

Setup

Install python if you haven't already

macOS

brew install python

Ubuntu

sudo apt-get update
sudo apt-get install python3
sudo apt-get install python3-pip

Install node if you haven't already

Mac

brew install node

Ubuntu

sudo apt-get install nodejs

Defining a function

A function has inputs and an output. The inputs are known as the "arguments", and the output is known as a "return value"

below is an example of a function in python

def multiply(a,b):
    return a * b

this is an example of the same function in javascript

function multiply(a,b) { 
    return a * b
}

This function takes two arguments (a and b), and returns the value of them multiplied together

Calling a function

In the above exercise you have simply defined a function, but you haven't asked python to call it. If you ran the program above, you wouldn't see any output in the terminal.

# This part of the code defines a function
def multiply(a,b):
    return a * b

# This part of the code then calls that function and assigns the variable x to its return value
x = multiply(8,9)

# This prints x to the terminal for humans to read
print(x)

in JavaScript that would look like this

// This part of the code defines a function
function multiply(a,b) { 
    return a * b
}

// This part of the code then calls that function and assigns the variable x to its return value
var x = multiply(8,9)

// This prints x to the terminal for humans to read
console.log(x)

Return vs Print

The function can also contain other logic and do other things. For example, you could write the function above like this:

def multiply(a,b):
    print("I'm multiplying two numbers")
    return a * b

This would both print to the terminal and return a value. The return is the very last logical thing that happens in the execution of a function. Once a return is called, no additional code can be run inside the function. The same is true in JavaScript (and all programming languages).

➡️ Try It

Complete the following assignment: https://classroom.github.com/a/9pY8aTQJ