JavaScript Overview and History

A programming language that is essential for web interactivity, working alongside HTML and CSS.

JavaScript's ability to support multiple programming styles like event-driven, functional, and imperative.

The standard that defines JavaScript's features and syntax and is managed by ECMA International.

The process of converting code into a form that the computer understands.

JavaScript's ability to handle data types without explicit declaration, meaning variables can change types.

A system that automatically manages memory allocation and deallocation, preventing memory leaks.

JavaScript's use of prototypes to create object relationships and inherit properties, instead of using classes.

Functions that can be treated like data and passed around like any other variable.

The first web browser that offered JavaScript support, paving the way for interactive web experiences.

A browser war competitor to Netscape Navigator, also known for its JavaScript implementation named JScript.

The standardization body responsible for defining the official specifications of JavaScript.

A Microsoft implementation of JavaScript, distinct from Netscape's original JavaScript.

The first version of a widely used open-source browser that challenged Internet Explorer's dominance and revived JavaScript development.

A standard for using JavaScript within XML documents, aiming to streamline data handling on the web.

An open-source project for a JavaScript runtime based on the ECMAScript 4 draft, but ultimately not adopted as the official standard.

A set of technologies, with JavaScript as the core, enabling web applications to load data dynamically without full page reloads.

A JavaScript library designed to simplify client-side scripting and provide powerful features for web development.

The JavaScript engine used in Google Chrome, known for its speed and efficiency.

A technique that compiles code just before execution, improving performance by optimizing code on the fly.

A JavaScript runtime environment that enables JavaScript to be used outside of web browsers.

A package manager that uses JavaScript, widely adopted for managing dependencies in Node.js projects.

A software component that executes JavaScript code.

Code written directly in JavaScript, without relying on external libraries or frameworks.

External libraries or tools that provide pre-written code for common JavaScript tasks.

Structured frameworks that provide a foundation for building JavaScript applications.

JavaScript's ability to run code based on events, such as user interactions, timing intervals, or network responses.

The process by which a single thread handles multiple tasks, making efficient use of resources.

The fundamental mechanism of how JavaScript executes code in response to messages.

A function without a name, often used for immediate execution or passing as an argument to another function.

A way for objects to inherit properties and methods from other objects, forming a chain of relationships.

A function can access and modify variables defined in its surrounding scope even after the outer function has finished executing.

An object can be designed by combining smaller, reusable objects or functions, promoting modularity and flexibility.

A function that can accept any number of arguments, making it adaptable for different scenarios.

A shorthand way to create arrays and objects, using a concise syntax.

A powerful way to search and manipulate text using patterns, similar to Perl.

An object that represents the eventual completion or failure of an asynchronous operation.

An elegant syntax for writing asynchronous code that looks and behaves like synchronous code.

A way to create reusable modules with specific functionalities that can be mixed into other objects.

The process of delegating functionality from one object to another, allowing for code reusability and flexibility.

A special keyword that defines a variable that can be reassigned, but its value cannot be changed after it's initialized.

JavaScript uses a dynamic typing system, where data types are associated with values rather than variables. This means variables can change their data type throughout the program.

JavaScript differentiates between expressions, which produce a value, and statements, which perform actions. Think of expressions as calculations and statements as instructions.

JavaScript's weakly typed nature allows automatic type conversions, where values are implicitly cast to a suitable type based on the operation.

JavaScript uses prototypes for object-oriented programming, where objects inherit properties and methods from their prototypes. This is different from class-based inheritance.

JavaScript's "eval" function allows executing code represented as strings at runtime. This can be used for dynamic functionality, but be cautious as it can pose security risks.

The binary + operator in JavaScript treats both operands as strings if at least one of them is a string, resulting in string concatenation.

The binary - operator in JavaScript ensures both operands are converted to numbers before performing subtraction.

JavaScript automatically inserts semicolons at the end of lines where they are omitted, allowing for concise code writing, but it can sometimes lead to unexpected behavior.

JavaScript's this keyword refers to the object that the function is called upon. However, its value can change based on the invocation context.

JavaScript functions can be called as methods of an object, with the this keyword bound to that object within the function's execution context.

JavaScript uses prototype-based inheritance, where objects inherit properties and methods from their prototypes, offering flexibility in object relationships.

In JavaScript, you can add properties and methods to the prototypes of built-in constructors (like Array and Object) for extending their capabilities.

In a function's scope, variables declared with "var" are accessible outside of the function, while variables declared with "let" or "const" have block-level scope (accessible only within the block they're declared in).

When scripts from a website can only perform operations within the browser's sandbox and cannot interact with the user's system directly.

A security mechanism that prevents scripts from one website from accessing data from another website. This helps protect sensitive information like usernames, passwords, and cookies.

A type of security attack where malicious code is injected into a website to steal user information or perform unauthorized actions.

A process of cleaning up potentially dangerous content from user input to prevent XSS attacks. HTML tags and scripts are often filtered.

A type of cross-site attack where an attacker tricks a user's browser into submitting actions to a target website without their knowledge.

An attack where a malicious website uses a "<iframe>" tag to load a page from a legitimate website and steal private data.

Involves adding an authentication token to both POST and GET requests for any response that contains private information.

A security mechanism that limits which resources a page can load, such as scripts or images. This helps to prevent XSS attacks.

A function that creates a private scope for variables and methods, allowing selective exposure of its members to the outside world, often used for creating modules.

A special function that can be paused and resumed, retaining its internal state between calls.

A mechanism that allows code in one JavaScript file to use code from another file.

A special keyword used to expose variables, functions, and classes from a module to other modules.

A keyword used to bring in variables, functions, and classes from other modules into the current module.

A block of code (generally a function) that executes when an object is created from a constructor function. Used for initializing object properties.

A property of a constructor function, used to store methods and properties that all instances created from the constructor function will inherit.

A method used to calculate the Greatest Common Divisor (GCD) of two integers.

A method used to calculate the Least Common Multiple (LCM) of two integers.

A way to swap the values of two variables in one line of code.

A type of function that is concise and uses an arrow (=>).

A JavaScript method that allows applying a function to each element of an array and creating a new array with the results.

A JavaScript method that allows executing a function for each element of an array.

A JavaScript method that sorts the elements of an array based on a provided comparison function.

A function that expects two arguments and returns a value that determines the order of sorting. It's used with the Array.sort() method.

JavaScript code can be directly inserted into HTML using document.write(), but is generally discouraged for performance and readability reasons. It can lead to unexpected behavior and overwrite existing document content.

A built-in JavaScript function that creates a new element based on the given tag name. For example, document.createElement('div') creates a new 'div' element.

A JavaScript function that adds the specified class name to the element's class attribute. For example, myElem.classList.add('highlight') adds highlight to the class attribute of myElem.

A JavaScript function that sets the value of an attribute for a specific element. For example, myElem.setAttribute('data-id', '123') sets a data-id attribute with a value of '123' to the element myElem.

A JavaScript function that appends a new element as a child to another element in the DOM. For example, document.body.appendChild(myElem) appends myElem as the last child of the body element.

A JavaScript function that selects the first element in the document that matches the provided CSS selector. For example, document.querySelector('.my-class') selects the first element with the class name 'my-class'.

A JavaScript function that selects all elements in the document that match the provided CSS selector and returns them as a NodeList. For example, document.querySelectorAll('.my-class') selects all elements with the class name 'my-class'.

A method for defining functions in JavaScript using a shorter syntax. Introduced in ECMAScript 2015 (ES6), they typically omit the function keyword.

A process in JavaScript where nested functions retain access to variables from their enclosing functions, allowing you to create private variables and data encapsulation.

A special variable in JavaScript within functions containing all arguments passed to the function. It allows functions to accept an arbitrary number of arguments.

A JavaScript feature that allows you to define a function that accepts a variable number of arguments using the ... syntax. It collects all remaining arguments into an array.

A JavaScript function that is executed immediately after it is defined. It helps create closures and avoids polluting the global scope.

A mechanism in JavaScript that allows creating objects based on predefined blueprints. It simplifies object creation and promotes code reusability.

A method within a class that is called when a new instance of the class is created using the new keyword. It initializes the object's properties.

A specialized type of function that exists within a class definition, representing an action or behavior that the object can perform.