Express.js Response Object
The Response object (res) specifies the HTTP response which is sent by an Express app when it gets an HTTP request.
What it does
- It sends response back to the client browser.
- It facilitates you to put new cookies value and that will write to the client browser (under cross domain rule).
- Once you res.send() or res.redirect() or res.render(), you cannot do it again, otherwise, there will be uncaught error.
Response Object Properties
Let’s see some properties of response object.
| Index | Properties | Description |
|---|---|---|
| 1. | res.app | It holds a reference to the instance of the express application that is using the middleware. |
| 2. | res.headersSent | It is a Boolean property that indicates if the app sent HTTP headers for the response. |
| 3. | res.locals | It specifies an object that contains response local variables scoped to the request |
Response Object Methods
Following are some methods:
Response Append method
Syntax:
This method appends the specified value to the HTTP response header field. That means if the specified value is not appropriate then this method redress that.
Examples:
Response Attachment method
Syntax:
This method facilitates you to send a file as an attachment in the HTTP response.
Examples:
Response Cookie method
Syntax:
This method is used to set a cookie name to value. The value can be a string or object converted to JSON.
Examples:
Response ClearCookie method
Syntax:
As the name specifies, the clearCookie method is used to clear the cookie specified by name.
Examples:
To set a cookie
To clear a cookie:
Response Download method
Syntax:
This method transfers the file at path as an “attachment” and enforces the browser to prompt user for download.
Example:
Response End method
Syntax:
This method is used to end the response process.
Example:
Response Format method
Syntax:
This method performs content negotiation on the Accept HTTP header on the request object, when present.
Example:
Response Get method
Syntax:
This method provides HTTP response header specified by field.
Example:
Response JSON method:
Syntax:
This method returns the response in JSON format.
Example:
Response JSONP method
Syntax:
This method returns response in JSON format with JSONP support.
Examples:
Response Links method
Syntax:
This method populates the response?s Link HTTP header field by joining the links provided as properties of the parameter.
Examples:
Response Location method
Syntax:
This method is used to set the response location HTTP header field based on the specified path parameter.
Examples:
Response Redirect method
Syntax:
This method redirects to the URL derived from the specified path, with specified HTTP status
Examples:
Response Render method
Syntax:
This method renders a view and sends the rendered HTML string to the client.
Examples:
Response Send method
Syntax:
This method is used to send HTTP response.
Examples:
Response sendFile method
Syntax:
This method is used to transfer the file at the given path. It sets the Content-Type response HTTP header field based on the filename’s extension.
Examples:
Response Set method
Syntax:
This method is used to set the response of HTTP header field to value.
Examples:
Response Status method
Syntax:
This method sets an HTTP status for the response.
Examples:
Response Type method
Syntax:
This method sets the content-type HTTP header to the MIME type.
Examples: