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Huh? You can treat state as arguments to your function. For a given function evaluation, the state is stable. The fact that state can be changed during event ha

by pacala 6y ago

Huh? You can treat state as arguments to your function. For a given function evaluation, the state is stable. The fact that state can be changed during event handling is 100% irrelevant to the evaluation. There is no dynamic scoping.

imtringued 6y ago
I feel you don't understand how React function components work. From a purely functional standpoint everything a function should have access to must be passed in as an argument. Any state that exists is always external to the function. Therefore hooks like useState can't exist because it creates state within a function. This is not only weird from a purely functional perspective it's also incredibly weird from a regular OOP perspective because that state should have been declared inside a class or struct. Therefore it is neither pure FP nor pure OOP. It's a random mix of both but it fools beginners into thinking that because it is not OOP it surely must be functional programming. The reality is that a component in React is still a class with internal state. React hooks are merely using a reference to "this" behind the scenes to store state but hooks are the only way to access that state. Therefore React hooks are basically a small DSL that adds features like dynamic scoping which is why lots of people think that this isn't regular Javascript anymore.
- deleted 6y ago
  [deleted]
- pacala 6y ago
  Can you please give an example of React hooks 'dynamic scoping'? See https://stackoverflow.com/a/22395580 https://stackoverflow.com/a/22395580 for an introduction to dynamic scoping. React hooks 'state' variables are scoped to a single function. They are not arbitrary variables, but represent inputs to the program. The mental model is a function that produces the same output given the same inputs. Think of a dropdown, where the associated state variable D my have values a, b or c, depending on what the user chooses. The render function simply does not care how the value of D was set, and renders the exact same jsx given a specific D value: jsxa for a, jsxb for b and jsxc for c. That is as pure as it gets. Furthermore, the dropdown state variable D never represents the intermediate computation of some other component[s], and it's never changed by other components arbitrarily based only on the variable name. The use of "dynamic scoping" to describe React Hooks state is unnecessarily imprecise, implying that a fairly well designed system is a specific kind of mess. Please don't engage in FUD. Tip: Never call setFoo functions from render code. Only call setFoo from event code.

by pacala 6y ago

imtringued 6y ago

I feel you don't understand how React function components work. From a purely functional standpoint everything a function should have access to must be passed in as an argument. Any state that exists is always external to the function. Therefore hooks like useState can't exist because it creates state within a function. This is not only weird from a purely functional perspective it's also incredibly weird from a regular OOP perspective because that state should have been declared inside a class or struct. Therefore it is neither pure FP nor pure OOP. It's a random mix of both but it fools beginners into thinking that because it is not OOP it surely must be functional programming. The reality is that a component in React is still a class with internal state. React hooks are merely using a reference to "this" behind the scenes to store state but hooks are the only way to access that state. Therefore React hooks are basically a small DSL that adds features like dynamic scoping which is why lots of people think that this isn't regular Javascript anymore.

deleted 6y ago
[deleted]
pacala 6y ago
Can you please give an example of React hooks 'dynamic scoping'? See https://stackoverflow.com/a/22395580 https://stackoverflow.com/a/22395580 for an introduction to dynamic scoping. React hooks 'state' variables are scoped to a single function. They are not arbitrary variables, but represent inputs to the program. The mental model is a function that produces the same output given the same inputs. Think of a dropdown, where the associated state variable D my have values a, b or c, depending on what the user chooses. The render function simply does not care how the value of D was set, and renders the exact same jsx given a specific D value: jsxa for a, jsxb for b and jsxc for c. That is as pure as it gets. Furthermore, the dropdown state variable D never represents the intermediate computation of some other component[s], and it's never changed by other components arbitrarily based only on the variable name. The use of "dynamic scoping" to describe React Hooks state is unnecessarily imprecise, implying that a fairly well designed system is a specific kind of mess. Please don't engage in FUD. Tip: Never call setFoo functions from render code. Only call setFoo from event code.