react-fun | React Fun - | Frontend Framework library
kandi X-RAY | react-fun Summary
kandi X-RAY | react-fun Summary
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QUESTION
I am making a simple react application which has some basic inputs like first name
, last name
etc..,
The state of the inputs are handled in context api like,
context.js
...ANSWER
Answered 2021-Apr-28 at 02:54if you just want to keep the initialValue always as the first time value, you need to do it like
QUESTION
I am making a very simple react application that has the basic details as inputs.
I am having these form values in context.
context.js
...ANSWER
Answered 2021-Apr-26 at 11:22you can use this approach to check whether any property exist in the json or it should be stored in the address
:
QUESTION
Okay, I think I might as well add here that I know that code doesn't look too good, but I thought it would do the job, so I would be glad if you could explain why not only it would not be a good practice if it worked, but why it doesn't work. I'd be glad to hear your solutions to the problem too!
I'm having a hard time understanding why the chunk of code below doesn't seem to work as intended by which I mean memoizing and
functional components' return values and not calling their functions on every
render. I thought that since
expression returns an object, it would be possible to simply memoize it and go with. Doesn't seem to work and I can't wrap my head around of as to why.
On a side note, I would also be thankful if you could explain why rendering component causes the
renders.current
value increment by two while only calling the console.log
once.
Thanks a lot for your help!
...ANSWER
Answered 2021-Apr-09 at 10:19For the second part of your question relating to why the value of render.current might be updating twice rather than once it might be because you are using React.StrictMode in your index.jsx file. Removing StrictMode did seem to fix the issue in this example. Also check out this link for more info.
As for the first issue, it seems that on clicking the re-render button neithr of the child components (First or Second) re-render. However, when we swap them not only do they re-render but the components are also unmounted and then re-mounted. You can see this behaviour in the above example, as well. Providing unique keys for both components seems to fix this issue. I'm also a beginner at React and not entirely sure of what's happening behind the scenes, however this is what I have gathered so far based on the documentation: When react finds that a child (say the first child) has a different type compared to what the type was on the previous render (in our case the type switches between First and Second) it unmounts the child node and all of its children, then re-mounts them, then continues with the rendering process. This is supported by the console logs we can see int the above example. By including unqiue keys we let react know that despite components First and Second being in different locations they are the same component after all. So, react doesn't bump into a scenario where a child has swapped types.
QUESTION
I have a list of students and I display them on the table. There are two buttons that indicate by which value should I sort the list (name or birthdate). When the button is clicked and I sort the list, the list itself is getting sorted, but it's not updating if I don't assign the list to the new list using Object.assign(newList, oldList)
and then update it by passing to the update state function updateList(newList)
. Here's my code:
ANSWER
Answered 2020-Dec-31 at 14:35As Brain mentioned: React determines if it should re-render or not based on the equality of previous props to the next props, and previous state to the next state. By mutating the original state array, the previous studentList has referential equality with the updated studentList and react will not detect that it needs to rerender.
So in order to change the list and to React detect the changes, the value of the array needs to be used (mutated), instead of its reference.
As Bergi hinted: alternative that copies the array by value
QUESTION
I am making a simple react app where there are two different div's
..
One with select input and selected list,
...ANSWER
Answered 2020-Nov-24 at 07:37React.createRef
is really only valid in class-based components. If used in a functional component body then the ref would be recreated each render cycle.- Don't use a DOM query selector to attach
onClick
listeners to DOM elements. These live outside react and you'd need to remember to clean them up (i.e. remove them) so you don't have a memory leak. Use React'sonClick
prop. - When the
selectedElements
are mapped you attach the same ref to each element, so the last one set is the one your UI gets.
- Use
React.useRef
in the functional component body to store an array of react refs to attach to each element you want to scroll into view. - Attach the
scrollSmoothHandler
directly to eachspan
'sonClick
prop. - Attach each ref from the ref array created in 1. to each mapped field set you want to scroll to.
Code
QUESTION
I am making a react app where I need to populate dynamic checkboxes from the data.
...ANSWER
Answered 2020-Oct-29 at 08:03You have no need to create another array with checked items. Just change your input like-
QUESTION
There are three buttons visible.
The first of which has no tooltip, and changes colour based on state and hover. The second has a tooltip, and the className is being overwritten, which results in the wrong colours being displayed. The third simply has the props re-ordered in the child component to solve the problem.
My question: Is this the expected behaviour? Do I really have to make className
the last prop so that it actually gets used?
ANSWER
Answered 2020-Sep-30 at 03:55In Material UI, you generally have to follow their recommendation for styling your components. One of which is to Override Style with classes prop
QUESTION
I have a component that renders multiple checkboxes. Each checkbox is handled dynamically with their checked
property to be assigned while rendering. I need to print/render the values of the checkboxes selected.
This is how a sample state looks like:
ANSWER
Answered 2020-Aug-17 at 19:46I forked your CodeSandbox and applied the fixes. You can find a working solution below.
https://codesandbox.io/s/react-functional-component-forked-gmwv0
There was quite a bit that needed to be changed, but I'll try to cover it as best as I can.
- You were referencing
this.setState
in your handleCheckboxChange, which doesn't work in a functional component. In a functional component, you use the 2nd argument of your useState hook, which in this case is equal tosetState
. Functional components don't usethis
for any internal methods. - There was invalid syntax inside of your render function. You need to make sure you're always returning a JSX object with a single top level wrapping component.
- The rest of the issues were inside of your handleCheckboxChange. Due to the asynchronous nature of setState, it is best to use the callback inside of setState which would be
setState((prevState) => {})
which will make sure you don't have stale state. You'll also need to return an object from this which will be your new state. - I updated the value of the checkbox (checked) to use the selected value that you calculate within this function.
- The final thing I did was update the mapping to properly return the correctly formatted state.
Final Solution
QUESTION
I am trying to wrap the NavigationContainer in React component for screen tracking, this approach worked well in V4 but fails in V5 unfortunately. The follow-up question is: will it be possible to wrap it in a function component and not in the react component to have the ability to use hooks? (must admit I am relatively new to react)
Will really appreciate any assistance
App.js
...ANSWER
Answered 2020-Aug-03 at 20:17App.js
QUESTION
I need to use the data coming from useContext to authenticate if the user logged in is Admin or not. But it gives the value "undefined" first and then after a delay of 5 seconds it gives the actual value. But by then, the code breaks because it cannot work with "undefined".
...ANSWER
Answered 2020-Jun-17 at 16:41You can setup a useEffect
hook to perform a side effect(redirect to "/") when state(userData) changes:
Replace:
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