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Unit 5
Term | Definition |
---|---|
User Interface (UI) | The "User Interface" or UI of an app refers to how a person (user) interacts with the computer or app. |
UI Elements | objects, like buttons, images, text boxes, pull down menus, screens and so on. |
UI Events | controls, like click, scroll, move mouse, type keyboard key, etc. |
Event-driven program | a program designed to run blocks of code or functions in response to specified events (e.g. a mouse click) |
Event handling | an overarching term for the coding tasks involved in making your app respond to events by triggering functions. |
Event listener | a command (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. |
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. |
Debugging | Finding and fixing problems in your code or algorithm |
Variable | In JavaScript (and most programming languages) the most primitive type of memory you can use is called a variable. It's called a variable because it's a piece of memory in which you can change what's stored - its value can vary. |
Expression | Any valid unit of code that resolves to a single value. (Variables can be assigned values that are the result of an expression.) |
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. For example 7+5 is interpreted differently from "7"+"5" |
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. Its global scope is typically derived from the variable being declared (created) outside of any function, object, or method. |
Local Variable | 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. |
String | Any sequence of characters between quotation marks |
Concatenate | to link together or join. Typically used when joining together text Strings in programming (e.g. "Hello, "+name) |
if Statement | The common programming structure that implements "conditional statements". |
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. |
Boolean | A single value of either TRUE or FALSE |
Boolean Expression | in programming, an expression that evaluates to True or False. |
while loop | a programming construct used to repeat a set of commands while a boolean condition is 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. |
List | A generic term for a programming data structure that holds multiple items. |
Array | A data structure in JavaScript used to represent a list. |
Key event | an event triggered by pressing or releasing a key on the keyboard. |
keyup | event type triggered when key is released on the keyboard |
keydown | event type triggered when key is pressed down on the keyboard |
event.key | Use event.key - from the event parameter of the onEvent callback function - to figure out which key was pressed. |
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. |
return | a command used to end execution of a function and resume execution at the point where the function was called. |
Return Value | A value sent back by a function to the place in the code where the function was called form - typically asking for value (e.g. getText(id)) or the result of a calculation or computation of some kind. |
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. |