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JavaScript Basics

JavaScript

The primary programming language of the web, primarily used for adding functionality to websites. JavaScript is a general purpose multi-paradigm programming language with dynamic typing.

Learn more: https://developer.mozilla.org/en-US/docs/Web/JavaScript

Paradigm

A style of programming. Oftentimes languages are built with a specific paradigm in mind, but JavaScript is known as a multi-paradigm language, because it allows for programming in a variety of paradigms. Some of the major paradigms of JavaScript include:

  • Event-driven: Functions can be made to respond to events, such as when a user clicks on an element or scrolls down the page.
  • Functional: Functions can be written as "pure functions", meaning functions that always have the same output for a given set of arguments and never produce side effects. Additionally, JavaScript supports first-class functions and higher-order functions. This means that functions can be treated as normal values, passed as arguments to other functions and returned from functions.
  • Object-oriented: Objects can be created as custom data stores and they can be made to inherit from each other.
  • Imperative: Programs can be written by explicitly describing the control flow, such as with loops and conditionals.
  • Declarative: Programs can be written by describing the desired output with implicit control flow. Oftentimes this is associated with functional programming (e.g. using the forEach function to loop over an array instead of a for loop).

Primitive

The most basic data types of a language. In JavaScript, there are 7 primitive types:

  • Number: Numeric values, including integers and decimal values.
  • BigInt: Integers too large to store in a number.
  • Boolean: A binary value of true or false.
  • String: A sequence of characters.
  • Symbol: A dynamically generated unique value.
  • Null: A nonexistent value.
  • Undefined: A value that has not been set.

JavaScript has a typeof operator that can get the type of a value as a lowercase string. However, do be aware that this function does have some special casing. For example, typeof function will return "function" even though functions are just objects.

Learn more: https://developer.mozilla.org/en-US/docs/Glossary/Primitive