State Remains Undefined in React

State Remains Undefined in React

Content Index :

State Remains Undefined in React
Tag : javascript , By : Singularity
Date : November 28 2020, 04:01 AM

it should still fix some issue I think you have used undeclared variable characters as error suggests Here:

No Comments Right Now !

Boards Message :
You Must Login Or Sign Up to Add Your Comments .

Share : facebook icon twitter icon

Looping through a JSON object's entries and through react state, getting 'state undefined'

Tag : javascript , By : keird
Date : March 29 2020, 07:55 AM
hope this fix your issue The problem is, the this inside the $.get() is not in the React's scope. And calling setState() inside render will throw an error. The following should help...
var App = React.createClass({
  getInitialState: function() {
    return {
      content: {},

  componentDidMount: function() {

  serverRequest: function() {
    var _this = this
    $.get(this.props.source, function(data) {
      _this.state.content = $.parseJSON(data);


  render: function() {
    return ( < div >

        Object.keys(this.state.content).map(function(key) {
          return <div > Key: {
          }, Value: {
          } < /div>;

      < /div >

Remains state on React

Tag : javascript , By : demize95
Date : March 29 2020, 07:55 AM
will help you First, you are doing a string concatenation rather than a sum.
You need to get a number from your input, for example through + operator:
this.setState({ input: +(event.target.value) });
this.setState(prevState => ({ sum: prevState.sum + prevState.input }));
state = { sum: 0, input: 0 };
import React, { Fragment, Component } from "react";

class Account extends Component {
  state = { sum: 0, input: 0 };
  input = event => {
    this.setState({ input: +(event.target.value) });
  Plus = () => {
    this.setState(prevState => ({ sum: prevState.sum + prevState.input }));
  Main = () => {
    this.setState(prevState => ({ sum: prevState.sum - prevState.input }));

  render() {
    return (
        <input value={this.state.input} onChange={this.input} />
        <br />
        <button onClick={this.Plus}>収入</button>
        <button onClick={this.Main}>支出</button>

export default Account;

React state component - Cannot read property 'state' of undefined

Tag : javascript , By : omaidog
Date : March 29 2020, 07:55 AM
Hope that helps searchProducts is a class method either bind it in constructor or use arrow functions (like in handleBrand). Currently your accessing the wrong value for this
searchProducts = () =>{}
    this.searchProducts = this.searchProducts.bind(this)

Why is my React state undefined even after setting the state in UseEffect hook?

Tag : javascript , By : Skee
Date : March 29 2020, 07:55 AM
I hope this helps . The first render (before useEffect done) paper is undefined (because you setState without params). So set state like this:
 const [paper, setPaper] = useState(null);   
 {paper && paper.articles.map(article => ( ....
 {paper ? paper.article.map(... : <WaitComponent/>
 if (typeof coord.lat !== 'undefined' && typeof coord.lng !== 'undefined')          
  url = `https://api.opencagedata.com/geocode/v1/json?q=${coord.lat}%2C${coord.lng}&key=${API_KEY}&pretty=1`;

React State remains immutable for states represented with lists

Tag : reactjs , By : Bas
Date : March 29 2020, 07:55 AM
may help you . I have a state represented by two arrangements. I must, at certain events, update one of them. The status update function is actually executed, but the status does not change, it remains with the same values before it is invoked. The status update does occur when I refresh the page, but not when the events that invoke the SetState occur. , You assigned wrong variable. Your state has
{listaSensor, listaNivel, sum}
Related Posts Related QUESTIONS :
  • How to use firestore TIMESTAMP to create time-stamp in JavaScript
  • Instantiate subclass without constructing
  • Outputing a created object in javascript to a server side JSON file
  • Transition the numeric labels in a bar chart
  • createBottomTabNavigator: hide just one tab from the tabBar
  • iife vs simple statement behavior with document.title
  • showDialogPopup Refresh Page after Click
  • Child component does not set the initial value passed from the parent: ReactJS
  • Nodejs javascript added to button not responding
  • Trying to define a promise.all
  • Python GEE to extract featurecollection timeseries from Landsat imageries
  • How to write negative binary number?
  • Unable to set property of individual object
  • Why Named Function Expression itself cannot assign Name to another Value?
  • How to reset scroll position on single page pagination
  • How to scroll to bottom of page, when a new message is sent - Socket.io
  • How to reconstruct audio blob from a base64 encoded String?
  • How to calculate numbers within an array of objects
  • Using JavaScript to change CSS properties of SVG circles for all circles that was not clicked
  • Is there value in propTypeing repeat required properties at every level of nested components?
  • Call function if variable does not exist in a filter
  • localStorage value doesn't get updated automatically
  • React not updating state with setState correctly inside promises
  • Direct native JavaScript or jQuery method to get containing block of an element
  • Dynamic JSON object to Html Table
  • How to send Id and file to same controller?
  • How to Make a jQuery Table Cell(td) clickable to Run a Function?
  • Prevent the duplicate function onchange event jQuery
  • Reactjs Input Upload doesn't return local URL
  • An unexpected 'StartObject' node was found when reading from the JSON reader. A 'PrimitiveValue' node was expected
  • How to filter a JSON Array, with an eventListener input value at keyup
  • How to separate the different properties of filter in css?
  • Why dont work change event of bootstrap input spinner?
  • How to hide overflow text content in react
  • Is there another way to write line 6
  • Cypress - how to find by text content?
  • How to setstate for the dynamic checkboxes in a loop in react?
  • Is display:none safe?
  • How to create a form to change part of a href url of a button?
  • Put many function inside function in Javascript
  • how to exit from loop after a ajax call
  • Do Angular Reactive Form Validator.min/max check Perform Type Conversions before checking the value?
  • How to Replace Text Within Script Tags Using JQuery
  • add variable to object if not undefined using short-hand
  • How can I effectively curve my items inside a list?
  • Add new record Keyboard Shortcut on Kendo Grid Mvc
  • Time and Date running on page
  • Looping through page links puppeteer doesn't return values from the newly loaded page
  • Problem with Navigator.geoLocation.getCurrentPosition not working
  • Trying to change the id of an element with Javascript
  • Embedded Schema Inserting Blank in Meteor using Collection2
  • avoid useEffect to render at first load?
  • Why is this CSS transition only working correctly on the some clicks? How to solve it?
  • Interpolated values does not reflect the latest values in an Angular app
  • Javascript classes define attribute in constructor or outside the class
  • How to block scroll event passing through to iframe until iframe is active?
  • What is the purpose of "constructor" method in javascript?
  • Stencil JS not working with non-default imports
  • Are frameworks misleadingly named for marketing purposes?
  • React <Redirect> after transition not working
  • shadow
    Privacy Policy - Terms - Contact Us © scrbit.com