Use JavaScript variable from file in React

Question

I'm trying to use some variables from a JavaScript file. My file is in the same path than my App component, and it has stored some value.

This is the js file, that simple, it only has the variable:

let num = 5;

On my App.js file I'm importing the js file this way:

import * as utils from './myjsfile';

And then on the componentDidMount methodI'm tryong to show it with an alert:

  componentDidMount() {
      alert(utils.num)
  }

But what I get is a × TypeError: Cannot read property 'num' of undefined

I've read some examples and this approach was supposed to work, I don't know what I'm doing wrong or if I have to do it in other way.

Thanks

Winter · Accepted Answer · 2018-06-07 11:01:52Z

5

You have to export it. Try

export let num = 5;

answered Jun 7, 2018 at 11:01

Winter

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Manoz · Accepted Answer · 2018-06-07 11:03:28Z

1

use export

export {num};

and import

import {num} from './myjsfile.js';

answered Jun 7, 2018 at 11:03

Manoz

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Comments

user10979902 · Accepted Answer · 2019-10-27 09:51:57Z

1

Export file lets.js:

let num_x = 5;
let num_y = 10;

export default { num_x, num_y };

import and use:

import * as nums from './lets';

let a = nums.default.num_y;
let b = nums.default.num_x;

answered Oct 27, 2019 at 9:51

user10979902

1 Comment

ScipioAfricanus Over a year ago

what is the purpose of 'default' here?

karthik · Accepted Answer · 2018-06-07 11:44:14Z

0

To access anything you have to export it first in node. Add export before let

answered Jun 7, 2018 at 11:44

karthik

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