A function specified as part of an event listener; it is written by the programmer but called by the system as the result of an event trigger.

A program designed to run blocks of code or functions in response to specified events (e.g. a mouse click)

An action that causes something to happen.

All values in a programming language have a "type" - such as a Number, Boolean, or String - that dictates how the computer will interpret it.

Any valid unit of code that resolves to a value.

The common programming structure that implements "conditional statements".

Dictates what portions of the code can "see" or use a variable, typically derived from where the variable was first created.

A variable whose scope is "global" to the program, it can be used and updated by any part of the code. Its global scope is typically derived from the variable being declared (created) outside of any function, object, or method.

A variable with local scope is one that can only be seen, used and updated by code within the same scope. Typically this means the variable was declared (created) inside a function -- includes function parameter variables.