React create constants file

Question

How to create constants file like: key - value in ReactJs,

ACTION_INVALID = \"This action is invalid!\"

and to use that in other components

Answer 1

You can simply create an object for your constants:

const myConstClass = {
    ACTION_INVALID: "This action is invalid!"
}

And then use it.

If you are bundling, you can export this object and then import for each component file.

Answer 2

One way to do that (not so different from other answers though) is to create a bare constants.js file and add your constants there.

module.exports = Object.freeze({
  ACTION_INVALID: 'This action is invalid',
  ACTION_VALID: 'Some other action',
});

Then you can import it

import ConstantsList from './constants';

and use

console.log(ConstantsList.ACTION_INVALID)

As the name suggests, Object.freeze() freezes objects and stops anyone from changing the values. Please note: if the values are objects themselves they are changeable (unless they are also frozen)

Answer 3

Expanding on Monad's answer, for situations where you don't want to type myConstClass all the time:

fileWithConstants.js:

export const ACTION_INVALID = "This action is invalid!"
export const CONSTANT_NUMBER_1 = 'hello I am a constant';
export const CONSTANT_NUMBER_2 = 'hello I am also a constant';

fileThatUsesConstants.js:

import { ACTION_INVALID } from 'path/to/fileWithConstants';

const errorMsg = ACTION_INVALID;

(Also, if Monad's way works better for you, I believe the convention is for 'MyConstClass' to start with a capital letter, since it's acting like a class in code.)

Answer 4

I'm not entirely sure I got your question but if I did it should be quite simple:

From my understanding you just want to create a file with constants and use it in another file.

fileWithConstants.js:

export const ACTION_INVALID = "This action is invalid!"
export const CONSTANT_NUMBER_1 = 'hello I am a constant';
export const CONSTANT_NUMBER_2 = 'hello I am also a constant';

fileThatUsesConstants.js:

import * as myConstClass from 'path/to/fileWithConstants';

const errorMsg = myConstClass.ACTION_INVALID;

If you are using react you should have either webpack or packager (for react-native) so you should have babel which can translate your use of export and import to older js.