Code 301 Class 05 Reading Notes

React Docs

  1. What is single responsibility principle and how does it apply to components? Using the same techniques for deciding if you should create a new funciton or object. A component should ideally only do one thing. If it starts to grow, it should be decomposed into smaller subcomponents.
  2. What does it mean to build a ‘static’ version of your application? Building components that reuse other components and pass data using props. props are a way of passing data from parent to child. Don’t use state to build a static version. State is reserved only for interactivity, that is, data that changes over time. Since this is a static version of the app, you don’t need it.
  3. Once you have a static application, what do you need to add? Start with building the components higher up in the hierarchy FilterableProductTable, or with the ones lower in it ProductRow. It’s easier to go top-down, and on larger projects, it’s easier to go bottom-up and write tests as you build.
  4. What are the three questions you can ask to determine if something is state?
    1. Is it passed in from a parent via props? If so, it probably isn’t state.
    2. Does it remain unchanged over time? if so, it probably isn’t state.
    3. Can you compute it based on any other state or props in your component? If so, it isn’t state.
  5. How can you identify where state needs to live?
    • Identify every component that renders something based on that state.
    • Find a common owner component (a single component above all the components that need the state in the hierarchy).
    • Either the common owner or another component higher up in the hierarchy should own the state.
    • If you can’t find a component where it makes sens to wn the state, create a new component solely for holding the state and add it somewhere in the hierarchy above the common owner component.

Higher-Order Functions

  1. What is a “higher-order function”? Functions that operate on other functions, either by taking them as arguments or by returning them.
  2. Explore the greaterThan function as defined in the reading. In your won words, what is line 2 of this function doing? parameter m is being determined if it is greater than argument n which will result in a boolean.
  3. Explain how either map or reduce operates, with regards to higher-order functions. The map method creates a new array populated with the result of calling a provided function on every element in the calling array. So map, itereates over the array, going over every element and creates a new array.

Things I want to know more about

More understanding on Map. I feel I get the general idea, but I would like to see more examples on various ways it can be used.

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