330 lines
11 KiB
Markdown
330 lines
11 KiB
Markdown
# protocol
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> Register a custom protocol and intercept existing protocol requests.
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Process: [Main](../glossary.md#main-process)
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An example of implementing a protocol that has the same effect as the
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`file://` protocol:
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```javascript
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const { app, protocol } = require('electron')
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const path = require('path')
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const url = require('url')
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app.whenReady().then(() => {
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protocol.registerFileProtocol('atom', (request, callback) => {
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const filePath = url.fileURLToPath('file://' + request.url.slice('atom://'.length))
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callback(filePath)
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})
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})
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```
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**Note:** All methods unless specified can only be used after the `ready` event
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of the `app` module gets emitted.
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## Using `protocol` with a custom `partition` or `session`
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A protocol is registered to a specific Electron [`session`](./session.md)
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object. If you don't specify a session, then your `protocol` will be applied to
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the default session that Electron uses. However, if you define a `partition` or
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`session` on your `browserWindow`'s `webPreferences`, then that window will use
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a different session and your custom protocol will not work if you just use
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`electron.protocol.XXX`.
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To have your custom protocol work in combination with a custom session, you need
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to register it to that session explicitly.
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```javascript
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const { session, app, protocol } = require('electron')
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const path = require('path')
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app.whenReady().then(() => {
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const partition = 'persist:example'
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const ses = session.fromPartition(partition)
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ses.protocol.registerFileProtocol('atom', (request, callback) => {
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const url = request.url.substr(7)
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callback({ path: path.normalize(`${__dirname}/${url}`) })
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})
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mainWindow = new BrowserWindow({ webPreferences: { partition } })
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})
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```
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## Methods
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The `protocol` module has the following methods:
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### `protocol.registerSchemesAsPrivileged(customSchemes)`
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* `customSchemes` [CustomScheme[]](structures/custom-scheme.md)
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**Note:** This method can only be used before the `ready` event of the `app`
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module gets emitted and can be called only once.
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Registers the `scheme` as standard, secure, bypasses content security policy for
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resources, allows registering ServiceWorker, supports fetch API, and streaming
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video/audio. Specify a privilege with the value of `true` to enable the capability.
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An example of registering a privileged scheme, that bypasses Content Security
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Policy:
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```javascript
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const { protocol } = require('electron')
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protocol.registerSchemesAsPrivileged([
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{ scheme: 'foo', privileges: { bypassCSP: true } }
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])
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```
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A standard scheme adheres to what RFC 3986 calls [generic URI
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syntax](https://tools.ietf.org/html/rfc3986#section-3). For example `http` and
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`https` are standard schemes, while `file` is not.
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Registering a scheme as standard allows relative and absolute resources to
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be resolved correctly when served. Otherwise the scheme will behave like the
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`file` protocol, but without the ability to resolve relative URLs.
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For example when you load following page with custom protocol without
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registering it as standard scheme, the image will not be loaded because
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non-standard schemes can not recognize relative URLs:
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```html
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<body>
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<img src='test.png'>
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</body>
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```
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Registering a scheme as standard will allow access to files through the
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[FileSystem API][file-system-api]. Otherwise the renderer will throw a security
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error for the scheme.
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By default web storage apis (localStorage, sessionStorage, webSQL, indexedDB,
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cookies) are disabled for non standard schemes. So in general if you want to
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register a custom protocol to replace the `http` protocol, you have to register
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it as a standard scheme.
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Protocols that use streams (http and stream protocols) should set `stream: true`.
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The `<video>` and `<audio>` HTML elements expect protocols to buffer their
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responses by default. The `stream` flag configures those elements to correctly
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expect streaming responses.
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### `protocol.registerFileProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` (string | [ProtocolResponse](structures/protocol-response.md))
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Returns `boolean` - Whether the protocol was successfully registered
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Registers a protocol of `scheme` that will send a file as the response. The
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`handler` will be called with `request` and `callback` where `request` is
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an incoming request for the `scheme`.
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To handle the `request`, the `callback` should be called with either the file's
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path or an object that has a `path` property, e.g. `callback(filePath)` or
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`callback({ path: filePath })`. The `filePath` must be an absolute path.
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By default the `scheme` is treated like `http:`, which is parsed differently
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from protocols that follow the "generic URI syntax" like `file:`.
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### `protocol.registerBufferProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` (Buffer | [ProtocolResponse](structures/protocol-response.md))
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Returns `boolean` - Whether the protocol was successfully registered
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Registers a protocol of `scheme` that will send a `Buffer` as a response.
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The usage is the same with `registerFileProtocol`, except that the `callback`
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should be called with either a `Buffer` object or an object that has the `data`
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property.
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Example:
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```javascript
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protocol.registerBufferProtocol('atom', (request, callback) => {
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callback({ mimeType: 'text/html', data: Buffer.from('<h5>Response</h5>') })
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})
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```
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### `protocol.registerStringProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` (string | [ProtocolResponse](structures/protocol-response.md))
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Returns `boolean` - Whether the protocol was successfully registered
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Registers a protocol of `scheme` that will send a `string` as a response.
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The usage is the same with `registerFileProtocol`, except that the `callback`
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should be called with either a `string` or an object that has the `data`
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property.
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### `protocol.registerHttpProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` [ProtocolResponse](structures/protocol-response.md)
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Returns `boolean` - Whether the protocol was successfully registered
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Registers a protocol of `scheme` that will send an HTTP request as a response.
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The usage is the same with `registerFileProtocol`, except that the `callback`
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should be called with an object that has the `url` property.
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### `protocol.registerStreamProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` (ReadableStream | [ProtocolResponse](structures/protocol-response.md))
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Returns `boolean` - Whether the protocol was successfully registered
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Registers a protocol of `scheme` that will send a stream as a response.
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The usage is the same with `registerFileProtocol`, except that the
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`callback` should be called with either a [`ReadableStream`](https://nodejs.org/api/stream.html#stream_class_stream_readable) object or an object that
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has the `data` property.
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Example:
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```javascript
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const { protocol } = require('electron')
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const { PassThrough } = require('stream')
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function createStream (text) {
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const rv = new PassThrough() // PassThrough is also a Readable stream
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rv.push(text)
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rv.push(null)
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return rv
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}
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protocol.registerStreamProtocol('atom', (request, callback) => {
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callback({
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statusCode: 200,
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headers: {
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'content-type': 'text/html'
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},
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data: createStream('<h5>Response</h5>')
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})
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})
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```
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It is possible to pass any object that implements the readable stream API (emits
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`data`/`end`/`error` events). For example, here's how a file could be returned:
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```javascript
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protocol.registerStreamProtocol('atom', (request, callback) => {
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callback(fs.createReadStream('index.html'))
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})
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```
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### `protocol.unregisterProtocol(scheme)`
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* `scheme` string
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Returns `boolean` - Whether the protocol was successfully unregistered
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Unregisters the custom protocol of `scheme`.
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### `protocol.isProtocolRegistered(scheme)`
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* `scheme` string
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Returns `boolean` - Whether `scheme` is already registered.
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### `protocol.interceptFileProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` (string | [ProtocolResponse](structures/protocol-response.md))
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Returns `boolean` - Whether the protocol was successfully intercepted
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Intercepts `scheme` protocol and uses `handler` as the protocol's new handler
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which sends a file as a response.
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### `protocol.interceptStringProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` (string | [ProtocolResponse](structures/protocol-response.md))
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Returns `boolean` - Whether the protocol was successfully intercepted
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Intercepts `scheme` protocol and uses `handler` as the protocol's new handler
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which sends a `string` as a response.
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### `protocol.interceptBufferProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` (Buffer | [ProtocolResponse](structures/protocol-response.md))
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Returns `boolean` - Whether the protocol was successfully intercepted
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Intercepts `scheme` protocol and uses `handler` as the protocol's new handler
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which sends a `Buffer` as a response.
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### `protocol.interceptHttpProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` [ProtocolResponse](structures/protocol-response.md)
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Returns `boolean` - Whether the protocol was successfully intercepted
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Intercepts `scheme` protocol and uses `handler` as the protocol's new handler
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which sends a new HTTP request as a response.
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### `protocol.interceptStreamProtocol(scheme, handler)`
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* `scheme` string
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* `handler` Function
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* `request` [ProtocolRequest](structures/protocol-request.md)
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* `callback` Function
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* `response` (ReadableStream | [ProtocolResponse](structures/protocol-response.md))
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Returns `boolean` - Whether the protocol was successfully intercepted
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Same as `protocol.registerStreamProtocol`, except that it replaces an existing
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protocol handler.
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### `protocol.uninterceptProtocol(scheme)`
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* `scheme` string
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Returns `boolean` - Whether the protocol was successfully unintercepted
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Remove the interceptor installed for `scheme` and restore its original handler.
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### `protocol.isProtocolIntercepted(scheme)`
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* `scheme` string
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Returns `boolean` - Whether `scheme` is already intercepted.
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[file-system-api]: https://developer.mozilla.org/en-US/docs/Web/API/LocalFileSystem
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