# 4.2. Document submission using HTML Forms

It is possible to write to a CouchDB document directly from an HTML form by using a document update function. Here’s how:

## 4.2.1. The HTML form

First, write an HTML form. Here’s a simple “Contact Us” form excerpt:

    <form action="/dbname/_design/ddocname/_update/contactform" method="post">
        <div>
            <label for="name">Name:</label>
            <input type="text" id="name" name="name" />
        </div>
        <div>
            <label for="mail">Email:</label>
            <input type="text" id="mail" name="email" />
        </div>
        <div>
            <label for="msg">Message:</label>
            <textarea id="msg" name="message"></textarea>
        </div>
    </form>

Customize the `/dbname/_design/ddocname/_update/contactform` portion of the form action URL to reflect the exact path to your database, design document and update function (see below).

As CouchDB no longer recommends the use of CouchDB-hosted web applications , you may want to use a reverse proxy to expose CouchDB as a subdirectory of your web application. If so, add that prefix to the `action` destination in the form.

Another option is to alter CouchDB’s CORS settings and use a cross-domain POST. Be sure you understand all security implications before doing this!

## 4.2.2. The update function

Then, write an update function. This is the server-side JavaScript function that will receive the `POST`-ed data.

The first argument to the function will be the document that is being processed (if it exists). Because we are using `POST` and not `PUT`, this should be empty in our scenario - but we should check to be sure. The `POST`-ed data will be passed as the second parameter to the function, along with any query parameters and the full request headers.

Here’s a sample handler that extracts the form data, generates a document _id based on the email address and timestamp, and saves the document. It then returns a JSON success response back to the browser.

    function(doc, req) {

        if (doc) {
            return [doc, toJSON({"error": "request already filed"})]
        }

        if !(req.form && req.form.email) {
            return [null, toJSON({"error": "incomplete form"})]
        }

        var date = new Date()
        var newdoc = req.form
        newdoc._id = req.form.email + "_" + date.toISOString()

        return [newdoc, toJSON({"success":"ok"})]
    }

Place the above function in your design document under the `updates` key.

Note that this function does not attempt any sort of input validation or sanitization. That is best handled by a validate document update function instead. (A “VDU” will validate any document written to the database, not just those that use your update function.)

If the first element passed to `return` is a document, the HTTP response headers will include `X-Couch-Id`, the `_id` value for the newly created document, and `X-Couch-Update-NewRev`, the `_rev` value for the newly created document. This is handy if your client-side code wants to access or update the document in a future call.

## 4.2.3. Example output

Here’s the worked sample above, using `curl` to simulate the form POST.

    $ curl -X PUT localhost:5984/testdb/_design/myddoc -d '{ "updates": { "contactform": "function(doc, req) { ... }" } }'
    {"ok":true,"id":"_design/myddoc","rev":"1-2a2b0951fcaf7287817573b03bba02ed"}

    $ curl --data "name=Lin&email=lin@example.com&message=I Love CouchDB" http://localhost:5984/testdb/_design/myddoc/_update/contactform
    *   Trying 127.0.0.1...
    * TCP_NODELAY set
    * Connected to localhost (127.0.0.1) port 5984 (#1)
    > POST /testdb/_design/myddoc/_update/contactform HTTP/1.1
    > Host: localhost:5984
    > User-Agent: curl/7.59.0
    > Accept: */*
    > Content-Length: 53
    > Content-Type: application/x-www-form-urlencoded
    >
    * upload completely sent off: 53 out of 53 bytes
    < HTTP/1.1 201 Created
    < Content-Length: 16
    < Content-Type: text/html; charset=utf-8
    < Date: Thu, 05 Apr 2018 19:56:42 GMT
    < Server: CouchDB/2.2.0-948a1311c (Erlang OTP/19)
    < X-Couch-Id: lin%40example.com_2018-04-05T19:51:22.278Z
    < X-Couch-Request-ID: 03a5f4fbe0
    < X-Couch-Update-NewRev: 1-34483732407fcc6cfc5b60ace48b9da9
    < X-CouchDB-Body-Time: 0
    <
    * Connection #1 to host localhost left intact
    {"success":"ok"}

    $ curl http://localhost:5984/testdb/lin\@example.com_2018-04-05T19:51:22.278Z
    {"_id":"lin@example.com_2018-04-05T19:51:22.278Z","_rev":"1-34483732407fcc6cfc5b60ace48b9da9","name":"Lin","email":"lin@example.com","message":"I Love CouchDB"}