如何在ReactJS文件中正确导入函数

Question

I'm having trouble importing a function in react. I used export default to export the function. However after importing it I tried to bind it in the render function but I got an error saying TypeError: Cannot read property 'bind' of undefined . Does this mean the function did not correctly import? How do I correctly import it in React?

import  onSignUp  from '../../functions/onsignup'
    class ModalExample extends React.Component {
    constructor(props) {
        super(props);
    }

     this.onSignUp=this.onSignUp.bind(this);
    }
    render(){
    return(...)
    }

Answer 1

It looks like you have an extra bracket in there, also, the imported function will just be onSignUp not this.onSignUp .

import  onSignUp  from '../../functions/onsignup'

class ModalExample extends React.Component {

  constructor(props) {
    super(props);
    this.onSignUp = onSignUp.bind(this);
  }

  render(){
    return(...)
  }
}

You should bind the function in the ctor or alternatively assign it in the class to onSignup like this:

import  onSignUp  from '../../functions/onsignup'

class ModalExample extends React.Component {

  constructor(props) {
    super(props);
  }

  onSignUp = onSignUp.bind(this);

  render(){
    return(...)
  }
}

(I think)

Answer 2

Does this mean the function did not correctly import?

Possibly yes.

How do I correctly import it in React?

import exportedFunction from './directorypath'; // if exported using default

import { exportedFunction } from './directorypath'; // if default not used while exporting.

A code snippet of the component would give a better picture of the problem.

Answer 3

Maybe you can put you declaration in the constructor like this referring to the onSignUp you imported instead of this.onSignUp that doesn't exists :

constructor(props) {
    super(props);
    this.onSignUp = onSignUp.bind(this);
}

Answer 4

Can you show us the function in the onSignUp file? you might not need to bind it depending on what function it is, however...

this.onSignp = this.onSignUp.bind(this);

Doing this in the constructor will assume you are initializing a new function not the one you are importing, use this instead.

this.onSignp = onSignUp.bind(this);

And make sure you are properly defining it from where you are declaring

Answer 5

If you are importing a function from out side of React class, then no need to bind it inside React class. You just import and use it. see the below..

functions/onsignup.js

function defined and export here.

const onSignUp = () =>{
// function code here
}

export default signup;

ModalExample.js

import the function here and use.

import React, {Componenet} from 'react';
import  onSignUp  from '../../functions/onsignup'

class ModalExample extends React.Component {
    constructor(props) {
        super(props);
    }


    render(){
      return(
         <button onClick={()=>onSignUp()} />
      )
    }
}