JavaScript Data Types and Data Structures Quiz

JavaScript Data Types and Data Structures

• JavaScript is a loosely typed language, meaning variables are not assigned to a particular data type.
• There are eight data types in JavaScript: seven primitives (String, Number, Boolean, Undefined, Null, BigInt, Symbol) and one non-primitive (JavaScript object).
• JavaScript objects include Arrays, Objects, Functions.

JS Array Methods

• The Array object stores a collection of multiple items under a single variable name.
• Array methods include Map, Filter, Reduce.
• The Map() method:
  • Maps an array of numbers using a function containing an argument.
  • Returns a new array with each element being the result of the callback function.
• The Reduce() method:
  • Can be used with or without an initial value.
  • The array parameter never changes during the process.
  • The value returned by reduce() is that of the last callback invocation.

Lists in React

• The Map() method can be used to reformat objects in an array.
• In React, the map method is used to transform lists, and a key is required for each item.
• Multiple components can be extracted, with a component tree.

JS Classes

• A class in object-oriented programming is like a blueprint or template for creating objects.
• A class should be defined before using it, and it is not hoisted.
• A JavaScript class is not an object, but a template for JavaScript objects.
• Properties and methods can be defined in a class, such as a Constructor() method.

Using a Class

• A class can be used to create objects, with the constructor method called automatically when a new object is created.
• React updates the Virtual DOM relative to the components, runs the diffing algorithm, and updates the real DOM.

React DOM

• The Virtual DOM is a copy of the actual DOM representation, used to hold updates made by the user and reflect them over to the original Browser DOM.
• ReactDOM provides DOM-specific methods, including render(), findDOMNode(), unmountComponentAtNode(), hydrate(), and createPortal().
• The render() function is used to render a single React Component, or several Components wrapped together.
• A "root" DOM node is used to manage everything inside it, and can be used in applications built with just React or when integrating React into an existing app.