# Introduction to JavaScript Functions

## What are functions?

Functions are a named list of statements and declarations with pre-defined input parameters and output values. Functions, in JavaScript, are just regular values and we can bind a constant or variable to a function object.

We already know that JavaScript is dynamically typed and hence does not require us to specify the types of a function's input parameters or output values.

function f2c(f) {return (f - 32) * 5 / 9}

The example above defines a function `f2c`

that converts Fahrenheit
temperatures to Celsius. The function signature (first line) tells us
the name of the function and the input parameters it accepts. In this
case the name is `f2c`

and it takes a single parameter `f`

.

const hundred = f2c(100)const fifty = f2c(50)

We can then use the defined function `f2c`

, invoke (call and execute)
with our Fahrenheit values and get Celsius degrees in return. Notice
how when we later use the `f2c`

function, we don't have to worry about
getting the mathematical conversion formula right. This is the major
selling point of splitting logic into small task specific functions.

If we ever decide to change the conversion implementation, we only
need to make changes in one place: the `f2c`

function.