Monday, 23 March 2020

A load of React Notes from my time dabbling with React

Overview of core:

this.state = stuff you can change
this.props = constants that come from the hierarchy.

Build / Flow locally:

  • yarn flow src

Lost / Where is that function from:

look for: conectRedux at the bottom of the file. - go to the class mentioned there.
Generally go to the bottom of the react file.


  • Dont use alert use window.sendError
  • Link tag: use 'to' not 'a'
  • Every list li ul element needs a key property key={uuid} NOT key="{uuid}"
  • Use button not a if it is a button.
  • Don't use Maps just use raw Objects instead:
  • If no state in a react component just use an arrow function.
  • Make react handle the loading case instead of blindly defaulting to empty list:
    • if (!teamsFetch || teamsFetch.pending) return <Loading />
    • if (teamsFetch.rejected) return <Error />
    • const rawTeams = (teamsFetch && teamsFetch.fulfilled && teamsFetch.value) || []
  • Use useMemo:
    • const memoisedValue = React.useMemo(() => doHeavyComputation(a, b), [a, b])
    • Must go before any returns. 
  • Don't modify this.props - instead call onChange and have the parent update it.  [...this.props.mylist, new_element]


Tests yarn add --dev jest
  • yarn jest
  • Jest test design: We don't tend to test the API is hit. Normally test the modals are called.

JS yarn prettify

yarn prettier --write find src | egrep jsx\\\\?$ --exclude passfort-types | grep -v passfort-types


Ignore JS Flow check add this on line before:

  • // $FlowFixMe
  • {/* $FlowFixMe */}

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