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TypeError: Cannot read property 'map' of undefined in React


By : Noy Sharlo
Date : September 17 2020, 05:00 AM
I hope this helps . It's because the key patientKeys doesn't exist inside your patientTabOptions object.
If you want to iterate through your object's keys you have to use the variable you've created called patientKeys
code :
patientTabOptions && patientKeys.map((item) => console.log(item))
patientTabOptions && Object.keys(patientTabOptions).map(key => patientTabOptions[key])
const data = patientTabOptions.ageGroup


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Uncaught TypeError: Cannot read property 'firstChild' of undefined in React, React-Bootstrap


By : user272063
Date : March 29 2020, 07:55 AM
this will help It was indeed a conflict with two different react versions. The react-bootstrap build I was using was bundled with react 0.14, while the react I was using was 0.13.3
Using v0.24.5 build of react-bootstrap instead, fixed the issue.

React - TypeError: Cannot read property 'map' of undefined


By : Mark Suter Mr Suter
Date : March 29 2020, 07:55 AM
I wish did fix the issue. Looks like you have not imported the charts.js file before using the charts array.
You could import the charts.js file where you use the ChartsGrid component and pass charts as a prop:
code :
import charts from './charts'
...
<ChartsGrid charts={charts} />
import charts from './charts'

export default class ChartsGrid extends React.Component{
  render() {
    return (
      <div className="grid">
        {charts.map((chart, i) => 
          <Chart {...this.props} key={i} i={i} chart={chart} />)}
      </div>
    )
  }
}

this.props undefined in React native: TypeError: Cannot read property 'title' of undefined


By : neo
Date : March 29 2020, 07:55 AM
Hope this helps I am trying to create a component that is a flatlist and to use probs to pass down some information to the component in the _renderItem function: , Solution
Fix typo.

React : TypeError: Cannot read property 'value' of undefined


By : afpsasda
Date : March 29 2020, 07:55 AM
Any of those help I am getting value from form in ReactJS but in meantime when I click on submit button it give me error TypeError: Cannot read property 'value' of undefined . Could someone Please check what problem I may face . , If you're using refs it should be this:
code :
const storeName = this.myInput.current.value;

How can i fix TypeError: Cannot read property 'map' of undefined REACT


By : Arnd
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further I've tried your code and it works well. Check the pictures below.
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