Here’s where immutability comes in: if you’re passing props into a PureComponent, you have to make sure that those props are updated in an immutable way. That means, if they’re objects or arrays, you’ve gotta replace the entire value with a new (modified) object or array. Just like with Bob – kill it off and replace it with a clone. If you modify the internals of an object or array – by changing a property, or pushing a new item, or even modifying an item inside an array – then the object or array is referentially equal to its old self, and a PureComponent will not notice that it has changed, and will not re-render. Weird rendering bugs will ensue.

An easy way to optimize a React component for performance is to make it a class, and make it extend React.PureComponent instead of React.Component. This way, the component will only re-render if its state is changed or if its props have changed. It will no longer mindlessly re-render every single time its parent re-renders; it will ONLY re-render if one of its props has changed since the last render.

Last week, I shared how to check if an input is empty with CSS. Today, let’s talk about the same thing, but with JavaScript.

You can do and impressive amount of form validation with just HTML attributes. You can make the user experience pretty clean and clear with CSS selectors.

the client form validation is the one I like a lot, because, for example, by adding required attribute to an input, I don’t need to write any additional JavaScript to warn a user, when the user submits a form without filling out the required fields

Frontend frameworks are a positive sum game! Svelte has no monopoly on the compiler paradigm either. Just like I think React is worth learning for the mental model it imparts, where UI is a (pure) function of state, I think the frontend framework-as-compiler paradigm is worth understanding. We're going to see a lot more of it because the tradeoffs are fantastic, to where it'll be a boring talking point before we know it.

Final Form makes the assumption that your validation functions are "pure" or "idempotent", i.e. will always return the same result when given the same values.

Final Form makes the assumption that your validation functions are "pure" or "idempotent", i.e. will always return the same result when given the same values. This is why it doesn't run the synchronous validation again (just to double check) before allowing the submission: because it's already stored the results of the last time it ran it.

If your React component’s render function is “pure” (in other words, it renders the same result given the same props and state)

Pony pureness, really? While polyfills are naughty, ponyfills are pure, just like ponies.

Polyfills are naughty as they patch native APIs, while ponyfills are pure and don't affect the environment.

With a RIMS, librarians don’t just manage a collection of primary sources; they develop reports and metrics by curating metadata from all departments, making the library not only the go-to spot for information on campus, but also the go-to spot for information about the campus.  

mixhumanmotives,nottopurifythem

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