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JavaScript SDK VM

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These methods only apply to projects embedded on a page.

All of the embed methods of the StackBlitz JS SDK automatically connect to the embedded StackBlitz VM, giving you programmatic access to the embedded project.

Use the VM to:

  • control the UI of an embedded StackBlitz project;
  • change the currently open file(s);
  • read and write files from the project’s virtual filesystem.

Getting access to the VM

SDK demo: using the VM

With embed methods

The embedProject, embedProjectId, and embedGithubProject methods of the SDK return a Promise resolving to an instance of the SDK’s VM class. We recommend using await in an async function to keep track of the VM instance. For example:

import sdk from '@stackblitz/sdk';

async function start() {
// Embeds a project and keeps track of the VM
const vm = await sdk.embedProjectId('embed', 'react-ts');

// Performs an action with VM
const deps = await vm.getDependencies();
await vm.applyFsDiff({
create: {
'hello.txt': 'Hello, this is a new file!',
'deps.txt': JSON.stringify(deps, null, 2),
},
destroy: [],
});
}

start();

With connect(iframe)

The SDK’s connect method can be used to retrieve the VM instance for an existing StackBlitz iframe.

ArgumentRequiredTypeDescription
iframeYesHTMLIframeElementAn iframe embedding a StackBlitz project.

Example:

import sdk from '@stackblitz/sdk';

const EMBED_ID = 'embed';

// Embeds iframe
sdk.embedProjectId(EMBED_ID, 'react-ts');

// Retrieves and uses the VM when clicking a button
document.getElementById('test-button').addEventListener('click', async () => {
const iframe = document.getElementById(EMBED_ID);
const vm = await sdk.connect(iframe);
const deps = await vm.getDependencies();
console.log(deps);
});

VM properties and methods

applyFsDiff(diff)

Updates project files. Returns a promise resolving to null.

ArgumentRequiredTypeDescription
diffYesObjectSpecifies files to create or delete
diff.createYesObjectObject with file paths as keys and contents as values
diff.destroyYesArrayFile paths of the files to delete
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When modifying existing files, the new content of the modified files must be provided in full.

Example:

await vm.applyFsDiff({
create: {
'index.js': `console.log('Hello World!')`,
'package.json': `{ "scripts": { "start": "node index.js" } }`,
},
destroy: ['test.js', 'error.log'],
});

getDependencies()

Gets the project’s defined dependencies. Returns a promise resolving to a ProjectDependencies object.

In EngineBlock projects, it returns the dependencies as resolved by the built-in package manager, with exact versions as values. For example: { 'react': '18.2.0' }.

Since 1.7.0: in project running on WebContainers, it reads the contents of the top-level package.json file and returns an object merging dependencies and devDependencies, with the original version specifiers as values. For example, { 'react': '^18.0.0' }.

Example:

const deps = await vm.getDependencies();

if (typeof deps['vue'] === 'string') {
console.log('Looks like a Vue.js project');
}

getFsSnapshot()

Gets a snapshot of the project files and their content. Returns a promise resolving to a ProjectFiles object.

Example:

const files = await vm.getFsSnapshot();
console.log(files); // { 'index.js': '…', 'package.json': '…', … }

editor.openFile(path)

Opens one or several files in tabs and/or split panes. Returns a promise resolving to null.

ArgumentRequiredTypeDescription
pathYesOpenFileOption (String or array of strings)Path(s) of file(s) to open

Example:

// opens a single file
await vm.editor.openFile('src/App.css');

// opens two editor panes
await vm.editor.openFile(['README.md', 'index.js']);

editor.setCurrentFile(path)

Since 1.7.0. Experimental: exact behavior may change.

Sets a project file as the currently selected file. Returns a promise resolving to null.

ArgumentRequiredTypeDescription
pathYesStringPath of the file to set as current
  • This may update the highlighted file in the file explorer, and the currently open and/or focused editor tab.
  • If the provided path does not match a currently open tab, a new editor tab will not open. See vm.editor.openFile to open files.

Example:

await vm.editor.setCurrentFile('src/App.css');

editor.setTheme(theme)

Since 1.7.0.

Changes the editor’s color theme. Returns a promise resolving to null.

ArgumentRequiredTypeDescription
themeYesUiThemeOption (String)The color theme name.
await vm.editor.setTheme('light');

editor.setView(view)

Since 1.7.0.

Changes the display mode of the project. Returns a promise resolving to null.

ArgumentRequiredTypeDescription
viewYesUiViewOption (String)The display mode name.
await vm.editor.setView('preview');

editor.showSidebar(visible)

Since 1.7.0.

Changes the display mode of the sidebar. Returns a promise resolving to null.

ArgumentRequiredTypeDescription
visibleNoBooleanUse true (default) to show the sidebar, false to hide.
await vm.editor.showSidebar(true);

preview.origin

A string with the origin (protocol and domain) of the preview iframe. Every project created with the embedProject method gets a unique preview URL.

Because it is unknown ahead of time if the project will run a web server (and if so, on which port), vm.preview.origin will always be null in projects running on WebContainers. You can use vm.preview.getUrl instead.

Example:

if (vm.preview.origin) {
console.log('Preview is running at ' + vm.preview.origin);
}

preview.getUrl()

Since 1.7.0. Experimental: exact behavior may change.

Gets the current preview URL. Returns a promise resolving to a string or to null.

The preview URL may not reflect the exact path of the current page if the user or page code has triggered a navigation within the preview iframe.

In WebContainers projects, the preview URL will be null initially, and until the project starts a web server.

Example:

const url = await vm.preview.getUrl();

if (url != null && url.startsWith('/about')) {
console.log('Looks like the About page!');
}

preview.setUrl(path)

Since 1.7.0. Experimental: exact behavior may change.

Changes the path of the preview URL. Returns a promise resolving to null.

ArgumentRequiredTypeDescription
pathYesStringA URL path starting with /.

The provided path must start with / and cannot change the origin of the preview URL.

In WebContainers projects, calls to vm.preview.setUrl will be ignored if there is no web server running currently.

Example:

// Navigates to the About page
await vm.preview.setUrl('/about');