Functions allow us to group commands and create new ones.
Treating a function as a command means to give it some data and ask it to produce a result.
This is commonly called *running* the function.
The terms calling, executing and invoking the function are also used. All of them mean the same thing.
As an example, imagine that you had a function called multiplyTwoNumbers.
Then you run it, you would give it the numbers 5 and 3 and it would return 15 to you as the result.
We can think of a function as divide into 3 parts.
- input: the data given to the function
- body: the commands (instructions) performed within the function
- output: the result sent out of a function
💡 The inputs to a function are also called arguments.
💡 The outputing of a result from a function is also called returning a result.
Here's how you can write the multiplyTwoNumbers function using our own made-up¹ language:
To call this function we write its name, followed by a pair of ().
💡 If you take a closer look, the multiply within multiplyTwoNumbers is another function! Functions can call other functions.
In the above code, the output of multiply is saved into a variable called result and then that variable is passed out as the output of multiplyTwoNumbers.
