Notes

Props

Props stands for properties. A system for passing data from a parent component to a child component. The goal is to customize or configure the child component.

Props are objects so the fields have to be called as methods: props.author for instance.

Functional components

Used anytime to show simple content to the user. (the card for example -- create JSX pass some props and return it).

Class components

For complex content, respond to user input, network request. Can use the state input.

Class components are not classes in terms of Ruby or Python, they are a Javascript Class. They also must be extended to a subclass (react component). And they must define a render method that returns some amount of JSX.

When components are reloaded they are also reloading the child components.gt

State

Rules

Only usable with class components (not always true)
state =/= props
State is a JS object that contains data relevant to a component
Updating state on a component causes the component to almost instantly rerender
State must be initialized when a component is created
State can only be updated with the setState function

Video 61: refactorisation on state and constructors, you can remove the whole constructor by passing a state to the class. => what is the state in a react application? Code is passed to Babel and understand the code that is compiled and extends + implements the constructor function.

     constructor(props) {
         super(props)
         this.state = { lat: null, errorMessage: '' }
     }

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