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• JavaScript


  A programming language that is both wonderful and horrible for beginners to learn
• JavaScript


  • You can build almost anything with it and get a job anywhere if you master it
  • It's weird, ugly, and surrounded by a dystopian Wasteland of Frameworks and libraries
• JavaScript was created in 1993 by Brendan Ike at Netscape
• At the time, the web browser was cutting edge technology that connected everybody on the planet via the World Wide Web
• Websites were completely static with pure HTML, so JavaScript was designed as an easy to use high level language to help developers make these websites interactive
• JavaScript is arguably the most popular language in the world and its standard implementation is called ecmascript and is the default language in all web browsers
• JavaScript is the only code that natively runs in a browser aside from webassembly
• JavaScript can also be run on a server thanks to tools like node.js and Dino
• Scripting language


  Code can be executed on the Fly by opening up the console in your browser Dev tools to run some code that changes the appearance of a website at any time
• Interpreted


  Code is executed line by line as opposed to other languages like C that are compiled ahead of time
• Under the hood of the browser there's an engine called V8 that makes JavaScript run extremely fast by taking your code and converting it to machine code with a process called Just in Time compilation
• Using JavaScript on a web page

  1. Have an HTML document

  2. Include a script tag

  3. Write code inside the tag directly or reference an external file with the source attribute

  4. Use console log to print to the standard output
• Variables


  Can be defined using let, const, or var
• let


  • Most common way to define variables today
  • Dynamically typed language, no data type annotations needed
  • Can be reassigned later
• const


  • Used for variables that cannot be reassigned later
• var


  • The original way to declare a variable, but should be ignored
• Lexical environment


  Determines where variables work and where they don't (global scope, local function scope, block scope)
• Functions


  One of the main building blocks in JavaScript<|>Can take input arguments and optionally return a value<|>Are just objects, can be used as Expressions
• this keyword


  • References an object, based on how a function is called (global scope, object, manually bound)
• Arrow functions


  • Don't have their own this value, always Anonymous, ideal for function Expressions
• Primitive vs Object


  Primitives are passed by value, objects are passed by reference
• Objects


  Defined with object literal syntax or constructor<|>Contain key-value pairs<|>Inherit properties from prototypes
• Classes


  Syntactic sugar for prototypal inheritance and objects<|>Define a Constructor, properties, Getters/Setters, and static methods
• Data structures


  Arrays, Sets, Maps, and more
• Garbage collection


  Automatically deallocates objects from memory when they're no longer referenced
• Event Loop


  Allows writing asynchronous code that runs in a separate thread pool while the rest of the application continues to execute
• Asynchronous code


  1. Use setTimeout for a simple example

  2. Callbacks can lead to callback hell

  3. Promises provide a better way to handle asynchronous code

  4. Async/await syntax makes asynchronous code more readable
• Modules


  Allow sharing code between files, with default exports and named exports
• npm


  The largest JavaScript package manager, downloads code into the node_modules folder
• Web development with JavaScript

  1. Use the Document Object Model to interact with HTML elements

  2. Listen to events and update the UI accordingly

  3. Front-end Frameworks provide declarative, reactive UI updates
• Module bundlers


  Tools like Veet or webpack that combine multiple JavaScript files into a single bundle for the browser
• Node.js


  Allows executing JavaScript code on the server
• Electron


  Combines Node.js with a browser to create full stack desktop apps with JavaScript
• React Native


  Allows creating iOS and Android apps with JavaScript
• If you want to make life easier, use a tool like TypeScript or ESLint that does static analysis to improve your code quality