Functions

We've been writing code that performs different actions, but sometimes you want to group code together to achieve a particular end. This is where functions come in.

A function is a block of code designed to perform a particular task. A function is executed when it is "invoked".

The syntax of a function looks like this:

function functionName (parameters) {
  // code to be executed
}

You can call a function whatever you want, just like a variable. You can also give a function different values every time you run it which are called "parameters".

To make the function run, we invoke it like so:

functionName();

Try it out

Let's write a function that adds two numbers together. We'll call it add. We want to add together two different numbers every time, so let's define two parameters to represent this, x and y.

function add (x, y) {
  // code to be executed
}

add(2, 3);

Notice I've invoked the function underneath, with the paremeters 2 and 3. Inside the function, try to console.log() your parameters and see what happens.

Now, we want to add these two numbers together, but it isn't enough just to write x + y, since we haven't told the function to return anything. It's time for a return statement. The return statement specifies the value to output.

function add (x, y) {
  return x + y;
}

add(2, 3);

Run this code, and hopefully you get the right answer!

Exercise

Write a function called multiply that multiplies two numbers together. It should take two numbers as parameters and return the answer.

Exercise

Go back and copy the code to your previous solution for printing the sum of numbers between 1 and 100. Put this code inside a function. Change the function so it accepts any two limits and prints the sum of all the numbers between those limits.

For example: addBetween(1,3) should print 6