Using CONSTANTS in JS is not problem free

index.js

/*
    I've seen this happen more than once. The data structure changes
    its implementation, and suddenly some other code that you forgot
    to update fails silently.
    
    Here, Constants used to have "TYPE" instead of "STATE". We
    updated it, but forgot to update the user of thing.
*/

// thing.js
export const Constants = {
    STATE_1: 'STATE_1',
    STATE_2: 'STATE_2'
}

export const thing = {
    state: Constants.STATE_1
}

// user-of-thing.js
import {thing, Constants} from './thing.js'

thing.type === Constants.TYPE_1 // true
thing.type === Constants.TYPE_2 // true 😱