Succeeded in fetching data, but it gives TypeError: Cannot read property ‘0’ of null

I have another problem today. ComponentDidMount seems to work fine(it brings data from the server), but when I try to use the data I received, it’d throw TypeError: Cannot read property ‘0’ of null. …

Is there a well-established way to update local state immediately without waiting for an API response in React/Redux?

TL;DR: Is there some well-known solution out there using React/Redux for being able to offer a snappy and immediately responsive UI, while keeping an API/database up to date with changes that can …

React Setstate callback called but render delayed

I just started to learn to react 2 days ago and I’m having a hard time with react’s setstate method, all I know is use revstate parameter if want to change state based on previous state, and callback …

React Native Updating State with this.setState

Hi I’m trying to update the state data value (data:[]) from API. the issue is from the line highlighted: this.setState({data.datasets[0].data.data:response.data.rates.AUD}) import React from ‘react’; …

How to re-render a component on each of multiple state changes?

I’m still learning JS/React, so it’s likely I’m doing this completely wrong. Any criticism is welcome. I have a Canvas with a drawning on it. I want to change the color of the drawning multiple times …

how to add and remove number without duplicate in the state object inside the array in Reactjs?

The below code which i’m using to add the data in the state the code is this.setState((state) => ({ …state, frequency: { …state.frequency, days: […state.frequency….

how to update the state before rendering the component?

I have this app that adds “persons” to a “phonebook”, and the user can update the person’s phone if the person already exists. but I want to know to handle the problem of when the …

reactjs setstate not working in function that has .map

Good Morning. Need help, i have the below script, the thing is the setState is not working, I think I’m missing something here? or Am i doing wrong. the “return” in the below is inside “…

Can a child method have change handler in React?

I was wondering why the child component with the changed value is not getting rendered here. Isn’t it a good idea to have a child handle its own changes or better to have the controller in the parent? This is the Child TodoItem As you can see the state is changed with handleChange() but this does not fire the render. I am also not too sure if another object can be assigned to an object of the state (let tempObj = thi.state.isComp). The functionality I am trying to achieve is check and uncheck a box and render accordingly. Answer What

Should I use setState conditional updates in componentDidUpdate in React 16?

I’m using React 16 and need to call a conditional setState inside componentDidUpdate. setState is executed asynchronously. So, usually, if I need to use state to compute my next state I should use updater function as an argument to setState. React 16 added a possibility to cancel a setState update by returning null from setState. So, should I use updater function to make a conditional setState? Code with updater: Code without updater: Answer I think there is no difference other than stylistically. Personally I prefer the second approach. Either way you will cause another render cycle so alternatively you could