Fundamentals of React

React Fundamental	Summary
React	A JS library for building dynamic UIs using components.
JSX	A syntax extension to JS that looks like HTML and makes defining UIs more intuitive vs. pure JS. JSX emits text in the page when a JS expression is surrounded with curly braces <div>{/* JS Expression */}</div>. JSX transpiles into a function call that returns a JS object, thus, JSX can be assigned to variables, passed as arguments to functions, etc. JSX can render an array of components, however, each component needs a key prop with a unique value. const catList = cats.map(c => <div key={cat.id}>{cat.name}</div>);.
Components	A user interface is defined by a hierarchy of components.
User-Defined Component	May be defined as a function or class but must be n