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Sandpack Client

This library serves as an interface to communicate with the bundler. The bundler itself is hosted on {version}-sandpack.codesandbox.io and is heavily cached by a CDN. We also included the necessary files under sandpack if you want to host the bundler yourself.

Install

To use it, you have to install a different package:

npm i @codesandbox/sandpack-client

or

yarn add @codesandbox/sandpack-client

Usage

The SandpackClient is a class implementation, you can import it from the package.

import { SandpackClient } from "@codesandbox/sandpack-client";

// There are two ways of initializing a preview, you can give it either an
// iframe element or a selector of an element to create an iframe on.
const client = new SandpackClient(
  "#preview", // iframe selector or element itself
  {
    files: {
      "/index.js": {
        code: `console.log(require('uuid'))`,
      },
    },
    entry: "/index.js",
    dependencies: {
      uuid: "latest",
    },
  }
  // We support a third parameter for advanced options,
  // you can find more info below
);

// When you make a change you can just run `updatePreview`,
// we'll automatically discover  which files have changed
// and hot reload them.
client.updatePreview({
  files: {
    "/index.js": {
      code: `console.log('New Text!')`,
    },
  },
  entry: "/index.js",
  dependencies: {
    uuid: "latest",
  },
});

If a package.json has been specified in the list of files that will be used as a source of truth. Otherwise, we infer dependencies and entry from it:

// We infer dependencies and the entry point from package.json
const PACKAGE_JSON_CODE = JSON.stringify(
  {
    title: "test",
    main: "index.js",
    dependencies: {
      uuid: "latest",
    },
  },
  null,
  2
);

// Give it either a selector or an iframe element
// as first argument, the second arguments are the files
const client = new SandpackClient("#preview", {
  files: {
    "/index.js": {
      code: `console.log(require('uuid'))`,
    },
    "/package.json": {
      code: PACKAGE_JSON_CODE,
    },
  },
});

SandboxInfo

The second argument in the constructor of SandpackClient is all sandbox info. It has this structure:

{
  /**
   * Files, keys are paths.
  **/
  files: {
    [path: string]: {
      code: string
    }
  },
  /**
   * Dependencies, supports npm and GitHub dependencies
  **/
  dependencies?: {
    [dependencyName: string]: string
  },
  /**
   * Default file to evaluate
  **/
  entry?: string,
  /**
   * The sandbox template to use, this is inferred from the files and package.json if not specified
  **/
  template?: string
}

ClientOptions

The third argument in the constructor of SandpackClient is extra options. Here you can pass custom bundling/evaluation options or instructions for what and how to render inside the iframe:

{
  /**
   * Paths to external resources
   */
  externalResources?: string[];
  /**
   * Location of the bundler. Defaults to `${version}-sandpack.codesandbox.io`
   */
  bundlerURL?: string;
  /**
   * Width/Height of the iframe.
   */
  width?: string;
  height?: string;
  /**
   * If we should skip the third step: evaluation. Useful if you only want to see
   * transpiled results
   */
  skipEval?: boolean;
  /**
   * Boolean flags to trigger certain UI elements in the bundler
   */
  showOpenInCodeSandbox?: boolean;
  showErrorScreen?: boolean;
  showLoadingScreen?: boolean;
}

Client API

The client instance has several helper functions you can call.

updatePreview

Send new content like files and dependencies to the preview. It will automatically hot update the preview with the new files and options. Accepts a single argument sandboxInfo of type SandboxInfo.

updateOptions

Updates the given options and then updates the preview. Accepts a single argument options of type ClientOptions.

dispatch

Dispatch an event to the bundler and all other listeners. Accepts a single argument, which is the data to send. The dispatch function will pass the internal id of the client, so only the bundler that performed the handshake with this client instance will respond.

client.dispatch({ type: "refresh" }); // sends a refresh action to the bundler

listen

Listens to events coming from the bundler that performed the handshake with this client instance. Uses the internal id to filter events coming from other bundlers.

client.listen((message) => {
  if (message.type === "status") {
    console.log(message.status);
  }
});

getCodeSandboxURL

Create a sandbox from the current files and return an object in this form:

{
  sandboxId: sandbox_id,
  editorUrl: `https://codesandbox.io/s/${sandbox_id}`,
  embedUrl: `https://codesandbox.io/embed/${sandbox_id}`,
}

Hosting the Bundler

note

You can also host the bundler by yourself, all necessary files are in the sandpack folder.

If you want to host the bundler yourself, you will need to do a few things.

  • The bundler is part of the codesandbox-client codebase: https://github.com/codesandbox/codesandbox-client
  • Clone the codesandbox-client and install the dependencies in the root folder (yarn install).
  • yarn build:deps to build some of the packages lerna needs for internal links.
  • create your instance of sandpack with yarn build:sandpack.

This creates a www folder in the root of codesandbox-client. That www folder is the sandpack folder sandpack-client connects to on {version}-sandpack.codesandbox.io. Once you have this hosted on your end you can pass bundlerURL when calling:

new SandpackClient(iframe, sandboxInfo, {
  bundlerURL: "https://your-hosted-version",
});

or, if you use sandpack-react, you can bundlerURL in the options of the Sandpack preset.

Why

There are few reasons for hosting the bundler like this, as opposed to having it exported as library code.

Security

The bundler evaluates and transpiles all files in an iframe under a different subdomain. This is important, because it prevents attackers from tampering with cookies of the host domain when evaluating code.

Performance

We heavily make use of Web Workers for transpilations. Almost all our transpilation happens in web workers, and there is no easy way yet to bundle this in a library.

Bundle Size

Another reason to host the bundler externally is because of code splitting: we split all our transpilers away and load them on-demand. If a user doesn't use sass we won't load the transpiler. This wouldn't be possible if we would give one big JS file as the library.

Offline Support

We use Service Workers to download all transpilers in the background, so the next time a user visits your website they don't have to download the bundler anymore and it can be used offline. This is possible because we host the service worker externally.