API Reference
APIs

preinitModule

Note

React-based frameworks frequently handle resource loading for you, so you might not have to call this API yourself. Consult your framework’s documentation for details.

preinitModule lets you eagerly fetch and evaluate an ESM module.

preinitModule("https://example.com/module.js", {as: "script"});

Reference

preinitModule(href, options)

To preinit an ESM module, call the preinitModule function from react-dom.

import { preinitModule } from 'react-dom';

function AppRoot() {
  preinitModule("https://example.com/module.js", {as: "script"});
  // ...
}

See more examples below.

The preinitModule function provides the browser with a hint that it should start downloading and executing the given module, which can save time. Modules that you preinit are executed when they finish downloading.

Parameters

  • href: a string. The URL of the module you want to download and execute.
  • options: an object. It contains the following properties:
    • as: a required string. It must be 'script'.
    • crossOrigin: a string. The CORS policy to use. Its possible values are anonymous and use-credentials.
    • integrity: a string. A cryptographic hash of the module, to verify its authenticity.
    • nonce: a string. A cryptographic nonce to allow the module when using a strict Content Security Policy.

Returns

preinitModule returns nothing.

Caveats

  • Multiple calls to preinitModule with the same href have the same effect as a single call.
  • In the browser, you can call preinitModule in any situation: while rendering a component, in an Effect, in an event handler, and so on.
  • In server-side rendering or when rendering Server Components, preinitModule only has an effect if you call it while rendering a component or in an async context originating from rendering a component. Any other calls will be ignored.