JavaScript Basics and Fundamentals

Practice flashcards covering JavaScript basics, including vocabulary, data types, control structures, functions, and object-oriented programming concepts.

Markup Languages

Languages like HTML and CSS used to describe and define elements within a document.

Programming Languages

Languages used to communicate instructions to a machine, control its behavior, and express algorithms.

Scripts

JavaScript programs that can be written directly in a web page’s HTML and run automatically as the page loads.

LiveScript

The initial name of JavaScript when it was first created.

ECMAScript

The independent specification that JavaScript follows, separate from its historical naming relation to Java.

JavaScript engine

A special program, sometimes called a "JavaScript virtual machine," that executes JavaScript code; examples include V8, SpiderMonkey, and Chakra.

V8

The specific JavaScript engine used in the Chrome and Opera browsers.

SpiderMonkey

The codename for the JavaScript engine used in the Firefox browser.

Parsing

The process where a JavaScript engine reads the script before conversion.

Compiling

The step in which an engine converts a script into machine language for fast execution.

Same Origin Policy

A safety limitation where JavaScript from one page may not access another page unless they share the same domain, protocol, and port.

src attribute

An attribute of the $<script>$ tag used to attach external JavaScript files to an HTML document.

innerHTML

A property used to access an HTML element and define its HTML content.

document.write()

A method used for testing to write directly into the HTML output; it deletes all existing HTML if used after the document is loaded.

window.alert()

A method that displays data in an alert box; this keyword is optional because it is the global scope object.

console.log()

A method used for debugging purposes to display data in the browser console.

window.print()

The only JavaScript method available to access output devices, used to print the content of the current window.

let

A keyword introduced in ES6 (2015) used to define a variable with restricted scope.

const

A keyword introduced in ES6 (2015) used to define a variable that cannot be reassigned.

Identifiers

Unique names used to identify JavaScript variables; they are case-sensitive and must begin with a letter, $$, or _.

Dynamic Types

A concept in JavaScript where the same variable can be used to hold different data types at different times.

Scientific Notation

A way to write extra large or small numbers using exponential form, such as $123e5$ or $123e-5$.

Booleans

A data type that can only have two values: true or false.

Arrays

Written with square brackets $[]$, these are objects used to store a collection of items separated by commas.

typeof

An operator used to find the data type of a JavaScript variable or expression.

undefined

The value and type of a variable that has been declared but has not been assigned a value.

null

A value representing "nothing" or something that does not exist; in JavaScript, its data type is incorrectly returned as "object."

Primitive Data

A single simple data value with no additional properties and methods, such as string, number, boolean, and undefined.

if statement

A fundamental control statement that allows JavaScript to make decisions and execute code only if a resulting value is true.

if…else if… statement

An advanced form of conditional statement that allows JavaScript to make a decision out of several possible conditions.

for loop

A compact looping form that includes initialization, a test condition, and an iteration statement.

for…in loop

A specific loop used to iterate through the properties of an object.

Function

A group of reusable code that can be called anywhere in a program to perform a specific task, promoting modularity.

return statement

An optional statement used to send a value from a function back to the calling program; it must be the last statement in the function.

Encapsulation

The OOP capability to store related information, including data and methods, together in an object.

Aggregation

The OOP capability to store one object inside another object.

Inheritance

The OOP capability of a class to rely upon another class for some of its properties and methods.

Polymorphism

The OOP capability to write one function or method that works in a variety of different ways.

Property

An attribute of an object; if it contains a value rather than a function, it is distinguished from a method.

Method

A function that is attached to an object and can be referenced by the "this" keyword.

new operator

An operator used to create an instance of an object, followed by a constructor method like Object(), Array(), or Date().

Constructor

A function used with the "new" operator to create and initialize a new object.

this keyword

A keyword used in user-defined functions to refer to the object that has been passed to the function.

with keyword

A shorthand keyword used to reference an object's properties or methods without repeatedly naming the object.