# Form-Data [](https://www.npmjs.com/package/form-data) [](https://gitter.im/form-data/form-data)
A library to create readable ```"multipart/form-data"``` streams. Can be used to submit forms and file uploads to other web applications.
The API of this library is inspired by the [XMLHttpRequest-2 FormData Interface][xhr2-fd].
// res – response object (http.IncomingMessage) //
res.resume();
});
```
For more advanced request manipulations ```submit()``` method returns ```http.ClientRequest``` object, or you can choose from one of the alternative submission methods.
### Custom options
You can provide custom options, such as `maxDataSize`:
``` javascript
var FormData = require('form-data');
var form = new FormData({ maxDataSize: 20971520 });
form.append('my_field', 'my value');
form.append('my_buffer', /* something big */);
```
List of available options could be found in [combined-stream](https://github.com/felixge/node-combined-stream/blob/master/lib/combined_stream.js#L7-L15)
### Alternative submission methods
You can use node's http client interface:
``` javascript
var http = require('http');
var request = http.request({
method: 'post',
host: 'example.org',
path: '/upload',
headers: form.getHeaders()
});
form.pipe(request);
request.on('response', function(res) {
console.log(res.statusCode);
});
```
Or if you would prefer the `'Content-Length'` header to be set for you:
Form-Data can recognize and fetch all the required information from common types of streams (```fs.readStream```, ```http.response``` and ```mikeal's request```), for some other types of streams you'd need to provide "file"-related information manually:
The `filepath` property overrides `filename` and may contain a relative path. This is typically used when uploading [multiple files from a directory](https://wicg.github.io/entries-api/#dom-htmlinputelement-webkitdirectory).
For edge cases, like POST request to URL with query string or to pass HTTP auth credentials, object can be passed to `form.submit()` as first parameter:
``` javascript
form.submit({
host: 'example.com',
path: '/probably.php?extra=params',
auth: 'username:password'
}, function(err, res) {
console.log(res.statusCode);
});
```
In case you need to also send custom HTTP headers with the POST request, you can use the `headers` key in first parameter of `form.submit()`:
Append data to the form. You can submit about any format (string, integer, boolean, buffer, etc.). However, Arrays are not supported and need to be turned into strings by the user.
**Note:** Because the output is of type Buffer, you can only append types that are accepted by Buffer: *string, Buffer, ArrayBuffer, Array, or Array-like Object*. A ReadStream for example will result in an error.
console.log('Upload successful! Server responded with:', body);
});
```
For more details see [request readme](https://github.com/request/request#multipartform-data-multipart-form-uploads).
#### node-fetch
You can also submit a form using [node-fetch](https://github.com/bitinn/node-fetch):
```javascript
var form = new FormData();
form.append('a', 1);
fetch('http://example.com', { method: 'POST', body: form })
.then(function(res) {
return res.json();
}).then(function(json) {
console.log(json);
});
```
#### axios
In Node.js you can post a file using [axios](https://github.com/axios/axios):
```javascript
const form = new FormData();
const stream = fs.createReadStream(PATH_TO_FILE);
form.append('image', stream);
// In Node.js environment you need to set boundary in the header field 'Content-Type' by calling method `getHeaders`
const formHeaders = form.getHeaders();
axios.post('http://example.com', form, {
headers: {
...formHeaders,
},
})
.then(response => response)
.catch(error => error)
```
## Notes
- ```getLengthSync()``` method DOESN'T calculate length for streams, use ```knownLength``` options as workaround.
- ```getLength(cb)``` will send an error as first parameter of callback if stream length cannot be calculated (e.g. send in custom streams w/o using ```knownLength```).
- ```submit``` will not add `content-length` if form length is unknown or not calculable.
- Starting version `2.x` FormData has dropped support for `node@0.10.x`.
- Starting version `3.x` FormData has dropped support for `node@4.x`.
## License
Form-Data is released under the [MIT](License) license.
