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

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.)