Send HTML text
A route returns a rendered or markup-like response directly to the client.
Express.js · Function
res.send
Sends an HTTP response from an Express route or middleware. Express formats strings as HTML, objects and arrays as JSON, and buffers as binary data.
How it works
Call res.send(body) inside a route handler to complete the HTTP response. Express selects the response representation from the value: strings are treated as HTML, objects and arrays as JSON, and buffers as binary data; the method returns the response object for chaining.
Syntax
res.send(body)Parameters
| Name | Type | Description |
|---|---|---|
body | String | Buffer | Object | Array | Boolean | undefined | The response content. Strings are sent as HTML, objects and arrays as JSON, and buffers as binary data; the documented type also includes Boolean and undefined. |
Returns
Response
Key points
- The required conceptual input is the response body supplied to the method.
- Express maps strings to HTML, objects and arrays to JSON, and buffers to binary responses.
- Calling the method completes the response sent to the client.
- Supported body values include buffers, strings, objects, booleans, and arrays.
- A status can be assigned before sending by chaining
res.status(code).send(body).
Common mistakes
- Do not pass the status as a positional argument; use
res.status(status).send(body)instead. - Use
res.sendStatus()when the response should contain only a status code. - A numeric argument can be interpreted as a status code, so convert numeric body data with
String(value).
Example: Send a string response
const express = require('express');
const app = express();
app.get('/user/:id', (req, res) => {
res.send(`user ${req.params.id}`);
});
app.listen(3000);Creates a route that sends a string response for a requested user ID.
When to use it
Return JSON data
An endpoint returns structured application data without manually serializing it.
Send a buffer
A handler needs to transmit already-created binary content.
Interview questions
QWhat does res.send() do, and what body types does it accept?
res.send(body) sends the HTTP response and returns the Response object. Express treats strings as HTML, objects and arrays as JSON, and buffers as binary data.
Follow-up: How would you return a JSON error with a non-200 status? Chain the status setter: res.status(500).send({ error: 'something blew up' }).
QHow does Express handle different response-body types?
The documented body argument may be a string, buffer, object, array, boolean, or undefined. The method chooses handling based on the supplied value, including HTML for strings and JSON for objects or arrays.
Follow-up: What should be done with a numeric body? Convert it to a string first, such as res.send(String(123)), so it is not treated as a status code.
QHow should a response status be set when using res.send()?
Set the status separately by chaining res.status(status).send(body). The older positional forms are deprecated, including res.send(body, status) and res.send(status) in Express 4.5.0, with the reversed form deprecated in 4.7.0.
Follow-up: Which method sends only a status code? Use res.sendStatus(status).
Related
res.status()res.sendStatus()res.json()res.end()