CODEWITHSUNDEEP
javascriptexportglobal-variables
uneasy
uneasy

Reputation: 619

JavaScript prevent changing exported object

Is there any way to prevent exported object to be changed later when it's imported ? I have my config.js helper that manages my config, and I want to export config but I want to only allow changes inside that config.js

let config = null

const refreshConfig = async () => {
  config = {something: "newvalue"}
}

export {config, refreshConfig}

but this way, I am allowed to change it somewhere else like: 

import {config} from 'config.js'

config.something = "changing it now"

how to prevent that scenario ?

Upvotes: 1

Views: 543

Answers (1)

T.J. Crowder
T.J. Crowder

Reputation: 1074405

You have a few options:

  1. If you don't need to change the config object's property values within the module, freeze it when loading it:

    config = Object.freeze({something: "new value"});

    You can still replace it (inside the module), you just can't change property values on it.

  2. Export a proxy that only allows allows retrieving information, not updating it.

    let realConfig = null;

const config = new Proxy({}, {
    get(target, propName) {
        return realConfig && realConfig[propName];
    }
});

    (You might choose to implement more proxy traps than just get.)

  3. Export a function that allows the caller to receive a defensive copy of the config, not the actual config.

#1 seems most applicable to the code in the question.

Upvotes: 2

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