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I have a child component wherein m updating the state and passing to parent

and in constructor i have set

mmtDLTh:false


mmtogDLTh()
{
  this.setState(prevState=>({mmtDLTh:!prevState.mmtDLTh}),()=>this.props.togtheme(mmtDLTh));
}

yet it says and in constructor i have set mmtDLTh is undefined throwing error at setState function

i have defined it in constructor i dont whats going wrong it may be in setState

Any help is appreciated.

mmtDLTh should be this.mmtDLTh in the callback to setState

Cannot read property 'Direction' of undefined · Issue #5687 · react , Requiring module "index.js", which threw an exception: TypeError: Cannot read property 'Direction' of undefined moduleThrewError  It should return exception in observable stream, then it can be handled in subsciber. Actual behavior: ERROR TypeError: Cannot read property 'throw' of undefined

though the error had vanished but then functionality wasnt working . it worked with the following

this.state.mmtDLTh

React: Building Modern Web Applications, defineProperty() method fails to modify or define an object property, then it throws exception, whereas the Reflect. first argument is the object that is used to define or modify a property • The second argument The default value is undefined. Dismiss Join GitHub today. GitHub is home to over 50 million developers working together to host and review code, manage projects, and build software together.

Set the mmtDLTh as state property

state = {
  mmtDLTh:false
}

In mmtoDLTh function toggle its value and in setState 's callback you can notify the parent by calling parent function passed to child as props.

mmtogDLTh()
{
  this.setState(
   prevState=>({
       mmtDLTh:!prevState.mmtDLTh
  }),()=> this.props.togtheme(this.state.mmtDLTh));
}

RNLocalize gets an undefined object on RNLocalize.initialContants , We used react-native-languages with i18n-js in our app to easly run-android now instantly throws me this exception undefined is not Test suite failed to run TypeError: Cannot read property 'initialConstants' of undefined  babel-node throws exception TypeError: Cannot read property 'canCompile' of undefined #9252 Closed philmetzger opened this issue Dec 28, 2018 · 4 comments

JavaScript Error Handling, A close look at the TypeError: null or undefined has no properties in more detail, looking at where it sits in the JavaScript Exception hierarchy as well as Null or Undefined Has No Properties errors are thrown, so let's get started! Unlike every other object which might be defined, the JavaScript engine  You have to avoid changing state with an undefined value. you are getting and undefined value and setting it to the state. your state will get changed and renders over an undefined value. First of all, you have to check if services.serviceImage has a value then you set the value to the state.

Error Boundaries – React, A class component becomes an error boundary if it defines either (or both) of the to render a fallback UI after an error has been thrown. that you can learn about unhandled exceptions as they happen in production, and fix them. Component names displayed in the stack traces depend on the Function.name property. That makes sense, otherwise cityname will be undefined (i missed this in my answer as it wasn't what was causing your original error). You had more than one issue with the original code, as SALEH pointed out in other answer's comment.

TypeError: can't define property "x": "obj" is not extensible , The JavaScript exception "can't define property "x": "obj" is not to add new properties to a non-extensible object throws a TypeError . In sloppy  After having the same issues, I managed to install react-native-fetch-blob and get rid of the Cannot read property 'DocumentDir of undefined' by: Following the installation steps (I used npm to install the module). Linking the package manually; I think the important part that I was missing even previously is to run pod install for iOS.

Comments
  • mmtDLTh should be this.mmtDLTh in the callback to setState non ?
  • it worked with "this" its resolved .but the expected result not seen
  • Not sure I understand your last remark, the code works but there are still bugs in your app ?
  • this has resolved the undefined error but expected behaviour not working lemme check if not ill post another question
  • ok, I made my comment in an answer in the meantime.
  • The issue with this approach is that your this.mmtDLTh and this.state.mmtDLTh will have different value after state change. Its better to put mmtDLTh in state. Your current code is working because on first time call prevState.mmtDLTh will be undefined and !prevState.mmtDLTh return true and from there onward your toggling the value of mmtDLTh in state.