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State Remains Undefined in React


State Remains Undefined in React

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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:
<Table 
                        characterData={characters}
                        removeCharacter={this.removeCharacter}
                    />
<Table 
                        characterData={this.state.characters}
                        removeCharacter={this.removeCharacter}
                    />

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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() {
    this.serverRequest()
  },

  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: {
            key
          }, Value: {
            this.state.content[key]
          } < /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) });
    console.log(this.state.input);
  };
  Plus = () => {
    this.setState(prevState => ({ sum: prevState.sum + prevState.input }));
  };
  Main = () => {
    this.setState(prevState => ({ sum: prevState.sum - prevState.input }));
  };

  render() {
    return (
      <Fragment>
        <h2>口座</h2>
        <h3>
          現在:&nbsp;
          {this.state.sum}
        </h3>
        <input value={this.state.input} onChange={this.input} />
        <br />
        <button onClick={this.Plus}>収入</button>
        <button onClick={this.Main}>支出</button>
      </Fragment>
    );
  }
}

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 = () =>{}
constructor(){
    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}
      {
        list,
        listaSensor,
        sum
      }
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