How to disable button in React.js

Question

I have this component:

import React from \'react\';

export default class AddItem extends React.Component {

add() {
    this.props.onButtonClick(this.input.         


        

Answer 1

this.input is undefined until the ref callback is called. Try setting this.input to some initial value in your constructor.

From the React docs on refs, emphasis mine:

the callback will be executed immediately after the component is mounted or unmounted