electron/docs/api/web-request.md
2018-09-14 14:57:01 +10:00

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Markdown

## Class: WebRequest
> Intercept and modify the contents of a request at various stages of its lifetime.
Process: [Main](../glossary.md#main-process)
Instances of the `WebRequest` class are accessed by using the `webRequest`
property of a `Session`.
The methods of `WebRequest` accept an optional `filter` and a `listener`. The
`listener` will be called with `listener(details)` when the API's event has
happened. The `details` object describes the request.
⚠️ Only the last attached `listener` will be used. Passing `null` as `listener` will unsubscribe from the event.
The `filter` object has a `urls` property which is an Array of URL
patterns that will be used to filter out the requests that do not match the URL
patterns. If the `filter` is omitted then all requests will be matched.
For certain events the `listener` is passed with a `callback`, which should be
called with a `response` object when `listener` has done its work.
An example of adding `User-Agent` header for requests:
```javascript
const { session } = require('electron')
// Modify the user agent for all requests to the following urls.
const filter = {
urls: ['https://*.github.com/*', '*://electron.github.io']
}
session.defaultSession.webRequest.onBeforeSendHeaders(filter, (details, callback) => {
details.requestHeaders['User-Agent'] = 'MyAgent'
callback({ cancel: false, requestHeaders: details.requestHeaders })
})
```
### Instance Methods
The following methods are available on instances of `WebRequest`:
#### `webRequest.onBeforeRequest([filter, ]listener)`
* `filter` Object (optional)
* `urls` String[] - Array of URL patterns that will be used to filter out the
requests that do not match the URL patterns.
* `listener` Function
* `details` Object
* `id` Integer
* `url` String
* `method` String
* `webContentsId` Integer (optional)
* `resourceType` String
* `timestamp` Double
* `uploadData` [UploadData[]](structures/upload-data.md)
* `callback` Function
* `response` Object
* `cancel` Boolean (optional)
* `redirectURL` String (optional) - The original request is prevented from
being sent or completed and is instead redirected to the given URL.
The `listener` will be called with `listener(details, callback)` when a request
is about to occur.
The `uploadData` is an array of `UploadData` objects.
The `callback` has to be called with an `response` object.
#### `webRequest.onBeforeSendHeaders([filter, ]listener)`
* `filter` Object (optional)
* `urls` String[] - Array of URL patterns that will be used to filter out the
requests that do not match the URL patterns.
* `listener` Function
The `listener` will be called with `listener(details, callback)` before sending
an HTTP request, once the request headers are available. This may occur after a
TCP connection is made to the server, but before any http data is sent.
* `details` Object
* `id` Integer
* `url` String
* `method` String
* `webContentsId` Integer (optional)
* `resourceType` String
* `timestamp` Double
* `requestHeaders` Object
* `callback` Function
* `response` Object
* `cancel` Boolean (optional)
* `requestHeaders` Object (optional) - When provided, request will be made
with these headers.
The `callback` has to be called with an `response` object.
#### `webRequest.onSendHeaders([filter, ]listener)`
* `filter` Object (optional)
* `urls` String[] - Array of URL patterns that will be used to filter out the
requests that do not match the URL patterns.
* `listener` Function
* `details` Object
* `id` Integer
* `url` String
* `method` String
* `webContentsId` Integer (optional)
* `resourceType` String
* `timestamp` Double
* `requestHeaders` Object
The `listener` will be called with `listener(details)` just before a request is
going to be sent to the server, modifications of previous `onBeforeSendHeaders`
response are visible by the time this listener is fired.
#### `webRequest.onHeadersReceived([filter, ]listener)`
* `filter` Object (optional)
* `urls` String[] - Array of URL patterns that will be used to filter out the
requests that do not match the URL patterns.
* `listener` Function
The `listener` will be called with `listener(details, callback)` when HTTP
response headers of a request have been received.
* `details` Object
* `id` Integer
* `url` String
* `method` String
* `webContentsId` Integer (optional)
* `resourceType` String
* `timestamp` Double
* `statusLine` String
* `statusCode` Integer
* `responseHeaders` Object
* `callback` Function
* `response` Object
* `cancel` Boolean
* `responseHeaders` Object (optional) - When provided, the server is assumed
to have responded with these headers.
* `statusLine` String (optional) - Should be provided when overriding
`responseHeaders` to change header status otherwise original response
header's status will be used.
The `callback` has to be called with an `response` object.
#### `webRequest.onResponseStarted([filter, ]listener)`
* `filter` Object (optional)
* `urls` String[] - Array of URL patterns that will be used to filter out the
requests that do not match the URL patterns.
* `listener` Function
* `details` Object
* `id` Integer
* `url` String
* `method` String
* `webContentsId` Integer (optional)
* `resourceType` String
* `timestamp` Double
* `responseHeaders` Object
* `fromCache` Boolean - Indicates whether the response was fetched from disk
cache.
* `statusCode` Integer
* `statusLine` String
The `listener` will be called with `listener(details)` when first byte of the
response body is received. For HTTP requests, this means that the status line
and response headers are available.
#### `webRequest.onBeforeRedirect([filter, ]listener)`
* `filter` Object (optional)
* `urls` String[] - Array of URL patterns that will be used to filter out the
requests that do not match the URL patterns.
* `listener` Function
* `details` Object
* `id` Integer
* `url` String
* `method` String
* `webContentsId` Integer (optional)
* `resourceType` String
* `timestamp` Double
* `redirectURL` String
* `statusCode` Integer
* `ip` String (optional) - The server IP address that the request was
actually sent to.
* `fromCache` Boolean
* `responseHeaders` Object
The `listener` will be called with `listener(details)` when a server initiated
redirect is about to occur.
#### `webRequest.onCompleted([filter, ]listener)`
* `filter` Object (optional)
* `urls` String[] - Array of URL patterns that will be used to filter out the
requests that do not match the URL patterns.
* `listener` Function
* `details` Object
* `id` Integer
* `url` String
* `method` String
* `webContentsId` Integer (optional)
* `resourceType` String
* `timestamp` Double
* `responseHeaders` Object
* `fromCache` Boolean
* `statusCode` Integer
* `statusLine` String
The `listener` will be called with `listener(details)` when a request is
completed.
#### `webRequest.onErrorOccurred([filter, ]listener)`
* `filter` Object (optional)
* `urls` String[] - Array of URL patterns that will be used to filter out the
requests that do not match the URL patterns.
* `listener` Function
* `details` Object
* `id` Integer
* `url` String
* `method` String
* `webContentsId` Integer (optional)
* `resourceType` String
* `timestamp` Double
* `fromCache` Boolean
* `error` String - The error description.
The `listener` will be called with `listener(details)` when an error occurs.