Event Driven Programming

Event Driven Programming

1. User Interface (UI)

   • UI EVents
     • or controls, like click, scroll, move mouse, type keyboard key, etc.
   • The user interface, or UI, of an app refers to how a person (user) interacts with their computer or app
     • UI Elements
       • or objects, like buttons, images, text boxes, pull down menus, screens and so on

2. Event Handling

   • Event Listener
     • Callback Function
       • 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 command (e.g., onEvent in App Lab) that can be set up to trigger a function when a particular type of event occurs on a particular UI element
       • while loop
         • a programming construct used to repeat a set of commands while a boolean condition it true
         • Models and Simulations
           • a program which replicates or mimics key features of a real world event in order to investigate its behavior without the cost, time, or danger of running an experiment in real life
         • for loop
           • a typical looping construct designed to make it easy to repeat a section of code using a counter variable. The for loop combines the creation of a variable, a boolean looping condition, and an update to the variable in one statement
       • console.log
         • a command that prints the given message to the console
   • an overarching term for the coding tasks involved in making your app respond to events by triggering functions
   • Users Trigger Events
     • events occur when users click a button, tap the screen, move the mouse, type a key on the keyboard, etc.
   • Events Trigger Code
     • when an event occurs or "fires" it can be used to trigger a particular javascript function

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

   • Data Type
     • all values in a programming language have a "type" - such as a Number, Boolean, or String - that dictates how the computer will interpret it (e.g., 7+5 is different from "7"+"5")
   • String
     • any sequence of characters between quotation marks
     • Concatenate
       • to link together or join, typically used when joining together text Strings in programming
   • Key event
     • an event triggered by pressing or releasing a key on the keyboard
       • event.key
         • use event.key - from the event parameter of the onEvent callback function - to figure out which key was pressed
           • keydown
             • event type triggered when key is pressed down on the keyboard
           • keyup
             • event type triggered when key is released on the keyboard
   • Return Value
     • a value sent back by a function to the place in the code where the function was called from--typically asking for value (e.g. getText(id)) or the result of a calculation or computation of some kind. Most programming languages have many built-in functions that return values, but you can also write your own

4. Syntax Errors

   • Debugging
   • a type of error occurring when things are misspelled or written in such a way the computer doesn't understand what you're trying to say

5. the program runs but doesn't do what you were thinking it would do

   • Logic Errors
     • going through code when given an error to figure out why the error is happening and then attempting to fix it; find and fixing problems in your code or algorithm

6. Variable

   • in most programming languages; a type of memory in which you can change what's stored - it's value can vary
     • Expression
       • any valid unit of code that resolves to a single value (variables can be assigned values that result from an expression)
       • Boolean Expression
         • in programming, an expression that evaluates to True or False
         • Boolean
           • a single value of either TRUE of FALSE
     • if statements
       • a way of checking to see if a condition is true and if it is execute a command
         • equal-equal: ==
           • for checking or testing to see what a value is
       • gets: =
         • assigning a value to a variable
       • Conditionals
         • another term for if statements -- statements that only run under certain conditions
       • Selection
         • a generic term for a type of programming statement (usually an if-statement) that uses a Boolean condition to determine, or select, whether or not to run a certain block of statements
   • Variable Scope
     • dictates what portions of the code can "see" or use a variable, typically derived from where the variable was first created
     • Global Variable
       • a variable whose scope is "global" to the program, it can be used and updated by any part of the code
     • a variable with local scope is one that can only be seen, used, and updated by code within the same scope
       • Local Variable

7. List

   • a generic term for a programming data structure that holds multiple items
     • Array
       • a data structure in JavaScript used to represent a list

8. Canvas

   • a user interface element to use in HTML/JavaScript which acts as a digital canvas allowing the programmatic drawing and manipulation of pixels, basic shapes, figures and images.