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JavaScript Cheatsheet

JavaScript (or JS) It is a popular programming language commonly used to create interactive effects within web browsers

variable A place to store values, can store any kind of information(data types): numbers, words, collections of data

undefined variable A variable that has no value

to declare variable To create a variable - done by using ‘ var variable-name = value ’

to initialize variable Set (give) some value to variable.

string A set of characters, word, phrase. To initialize variable with a string you need to put this string into quotes.

boolean Boolean variable represent a logical values True or False

array An ordered list of values, can store different type of data inside

operator Mathematical operators, such as: +, -, *, /, >, <, = etc

comments Comments are some notes that you can leave for yourself or another person, the note that computer will not read. You can write a comment on a new line or on the same line after code as so: //I’m your comment Single line comment starts with // Multi line comment are placed between /* .. */

function A separable, reusable piece of code. It takes some input do some manipulation on it and return us output

to declare function To create a function

argument A value input that functions can accept

if/else statement ‘If’ used to decide which lines of code to execute, ‘else’ - to give alternative set of instructions. Example: if(x > 5) {console.log”X bigger than 5”}; else {console.log”X smaller than 5”};

while loop It repeats code over and over again until some condition is met

for loop This loop is similar to ‘while loop’, just with set amount of repetition. You declare counter in the statement as so: for(var i = 0; i < 5; i++){do something 5 times};

infinite loop A loop that does not stop and it’s a loop that you need to avoid. Each loop should have some condition so it can stop.

object A collection of properties

event A type of object that is created when user interacts with web page. For example, JavaScript creates an event when user clicks on a button.

CSS Stands for Cascading Style Sheets. CSS describes how HTML elements are to be displayed on screen. It is presentation.

HTML Stands for Hyper Text Markup Language. It is a structure of the elements on the page.

DOM Stands for Document Object Model. It defines the logical structure of documents and the way a document is accessed and manipulated.

scope Scope is the set of variables, objects, and functions that you can access

console A method of interacting with the system. In order to write to the browser console, you could use console.log(‘Hello World’). This would write Hello World in the browser console.