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Installation

MobX works in any ES5 environment, which includes browsers and NodeJS.

There are two types of React bindings, mobx-react-lite supports only functional components, whereas mobx-react also supports class based components. Append the appropriate bindings for your use case to the Yarn or NPM command below:

Yarn: yarn add mobx

NPM: npm install --save mobx

CDN: https://cdnjs.com/libraries/mobx / https://unpkg.com/mobx/dist/mobx.umd.production.min.js

Use spec compliant transpilation for class properties

⚠️ Warning: When using MobX with TypeScript or Babel, and you plan to use classes; make sure to update your configuration to use a TC-39 spec compliant transpilation for class fields, since this is not the default. Without this, class fields cannot be made observable before they are initialized.

  • TypeScript: Set the compiler option "useDefineForClassFields": true.
  • Babel: Make sure to use at least version 7.12, with the following configuration: 
    {
    // Babel < 7.13.0
    "plugins": [["@babel/plugin-proposal-class-properties", { "loose": false }]],
    
    // Babel >= 7.13.0 (https://babeljs.io/docs/en/assumptions)
    "plugins": [["@babel/plugin-proposal-class-properties"]],
    "assumptions": {
        "setPublicClassFields": false
    }
}

For verification insert this piece of code at the beginning of your sources (eg. index.js)

if (!new class { x }().hasOwnProperty('x')) throw new Error('Transpiler is not configured correctly');

MobX on older JavaScript environments

By default, MobX uses proxies for optimal performance and compatibility. However, on older JavaScript engines Proxy is not available (check out Proxy support). Examples of such are Internet Explorer (before Edge), Node.js < 6, iOS < 10, Android before RN 0.59, or Android on iOS.

In such cases, MobX can fallback to an ES5 compatible implementation which works almost identically, although there are a few limitations without Proxy support. You will have to explicitly enable the fallback implementation by configuring useProxies:

import { configure } from "mobx"

configure({ useProxies: "never" }) // Or "ifavailable".

MobX and Decorators

If you have used MobX before, or if you followed online tutorials, you probably saw MobX with decorators like @observable. In MobX 6, we have chosen to move away from decorators by default, for maximum compatibility with standard JavaScript. They can still be used if you enable them though.

Development vs production

Unless you're using pre-build distribution ending with .[production|development].min.js, Mobx uses process.env.NODE_ENV variable to detect the environment. Make sure it's set to "production" on production. This is usually done by your favourite bundler: webpack Rollup Browserify Brunch

Most of the safety checks, like enforceAction and similar, happens on development only.

MobX on other frameworks / platforms

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