`this` not being passed to function when using bind() call() or apply()

Question

I'm using React and inside my componentDidMount() {} I'm calling an imported function and want to access this.setState within it.

Within componentDidMount, When I console.log(this), I get the component as expected.

But if I run myFunction.call(this), console.log(this) inside myFunction returns undefined.

Any ideas why this is not being passed correctly?

edit1: adding code.

Component:

class Navbar extends React.Component {
    componentDidMount() {
        myFunction.call();
    }
}

myFunction.js:

export const myFunction = () => {
    console.log('this:', this);
}

Console output:

this: undefined

edit2: some people flagged this as a duplicate of "can i bind arrow functions" but myFunction is an arrow function and even if I call it directly instead of using .call() it produces the same result: this is undefined.

`this` in the context you're invoking the method is `undefined`, you should pass a reference to the target component instead of `this`. — Teemu, Jun 19 '19 at 17:06
How about return a value from the imported function and use the returned value to set the state ? even if you need to access something from the component state or props you can pass it as an argument — Asaf Aviv, Jun 19 '19 at 17:06
commenters are working in the dark here, please post the code. — Matt Pengelly, Jun 19 '19 at 17:24

score 1 · Answer 1 · answered Jun 19 '19 at 23:29

1

Bind the imported function in the constructor:

import { myFunction } from './path/to/myFunction';

class Navbar extends React.Component {
    constructor() {
       /* other constrcutor code */
       myFunction = myFunction.bind(this);
    }
    componentDidMount() {
       myFunction();
    }
}

In your myFunction.js, convert the ES6 arrow function to a regular ES5 function (see Can you bind arrow functions?):

export const myFunction = function() {
    console.log('this:', this);
}

answered Jun 19 '19 at 23:29

connexo

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when I do this it errors within the constructor saying myFunction is not defined – remjx Jun 20 '19 at 00:59
Well then clearly your import is either not there or it does not work. That, though, cannot be a result of my suggested changes. – connexo Jun 20 '19 at 05:49

`this` not being passed to function when using bind() call() or apply()

1 Answers1