Agenda

Named Functions

Anonymous Functions

Function Declarations

Arrow Functions

Callbacks

Overview of Functions

In some languages, they might call them “methods”. In JavaScript, they’re called “functions”. But they’re usually the same thing: A block of re-usable code that has an identifier. The logic of how they work is mostly the same, but how we code them is significantly different.

You already know how to use functions that are part of the language: so far you’ve learned alert(), confirm(), prompt(), typeof(), Number(), Boolean(), String(), and probably others in your explorations.

You can also create functions, of course — similar to how you would create function in Python.

There are different kinds of functions:

• named functions have a specific name that you can use to call them anywhere in your code
• anonymous functions have no name and are generally assigned to a variable or property

There are different techniques we can use to create functions:

• function declarations are used to define a named function that is loaded when its file is loaded, and are only executed when they are invoked later in the code
• function expressions allow you to assign a named or anonymous function to a variable or property
• arrow functions are a shorthand syntax for anonymous functions
• callback functions are functions that are passed to another function with the intention that the callback function will be invoked somewhere inside the function that receives the callback

When creating functions, it’s also important to understand the visibility of variables, parameters, and the functions themselves (scope).