How to send a JSON object using html form data

Question

So I've got this HTML form:

<html>
<head><title>test</title></head>
<body>
    <form action="myurl" method="POST" name="myForm">
        <p><label for="first_name">First Name:</label>
        <input type="text" name="first_name" id="fname"></p>

        <p><label for="last_name">Last Name:</label>
        <input type="text" name="last_name" id="lname"></p>

        <input value="Submit" type="submit" onclick="submitform()">
    </form>
</body>
</html>

Which would be the easiest way to send this form's data as a JSON object to my server when a user clicks on submit?

UPDATE: I've gone as far as this but it doesn't seem to work:

<script type="text/javascript">
    function submitform(){
        alert("Sending Json");
        var xhr = new XMLHttpRequest();
        xhr.open(form.method, form.action, true);
        xhr.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
        var j = {
            "first_name":"binchen",
            "last_name":"heris",
        };
        xhr.send(JSON.stringify(j));

What am I doing wrong?

Answer 1

Get complete form data as array and json stringify it.

var formData = JSON.stringify($("#myForm").serializeArray());

You can use it later in ajax. Or if you are not using ajax; put it in hidden textarea and pass to server. If this data is passed as json string via normal form data then you have to decode it. You'll then get all data in an array.

$.ajax({
  type: "POST",
  url: "serverUrl",
  data: formData,
  success: function(){},
  dataType: "json",
  contentType : "application/json"
});

Answer 2

HTML provides no way to generate JSON from form data.

If you really want to handle it from the client, then you would have to resort to using JavaScript to:

gather your data from the form via DOM
organise it in an object or array
generate JSON with JSON.stringify
POST it with XMLHttpRequest

You'd probably be better off sticking to application/x-www-form-urlencoded data and processing that on the server instead of JSON. Your form doesn't have any complicated hierarchy that would benefit from a JSON data structure.

Update in response to major rewrite of the question…

Your JS has no readystatechange handler, so you do nothing with the response
You trigger the JS when the submit button is clicked without cancelling the default behaviour. The browser will submit the form (in the regular way) as soon as the JS function is complete.

Answer 3

You can try something like:

<html>
<head>
    <title>test</title>
</head>

<body>
    <form id="formElem">
        <input type="text" name="firstname" value="Karam">
        <input type="text" name="lastname" value="Yousef">
        <input type="submit">
    </form>
    <div id="decoded"></div>
    <button id="encode">Encode</button>
    <div id="encoded"></div>
</body>
<script>
    encode.onclick = async (e) => {
        let response = await fetch('http://localhost:8482/encode', {
                method: 'GET',
                headers: {
                    'Content-Type': 'application/json',
                },
        })

        let text = await response.text(); // read response body as text
        data = JSON.parse(text);
        document.querySelector("#encoded").innerHTML = text;
      //  document.querySelector("#encoded").innerHTML = `First name = ${data.firstname} <br/> 
      //                                                  Last name = ${data.lastname} <br/>
      //                                                  Age    = ${data.age}`
    };

    formElem.onsubmit = async (e) => {
      e.preventDefault();
      var form = document.querySelector("#formElem");
     // var form = document.forms[0];

        data = {
          firstname : form.querySelector('input[name="firstname"]').value,
          lastname : form.querySelector('input[name="lastname"]').value,
          age : 5
        }

        let response = await fetch('http://localhost:8482/decode', {
                method: 'POST', // or 'PUT'
                headers: {
                    'Content-Type': 'application/json',
                },
                body: JSON.stringify(data),
        })

        let text = await response.text(); // read response body as text
        document.querySelector("#decoded").innerHTML = text;
    };
</script>
</html>

Answer 4

I'm late but I need to say for those who need an object, using only html, there's a way. In some server side frameworks like PHP you can write the follow code:

<form action="myurl" method="POST" name="myForm">
        <p><label for="first_name">First Name:</label>
        <input type="text" name="name[first]" id="fname"></p>

        <p><label for="last_name">Last Name:</label>
        <input type="text" name="name[last]" id="lname"></p>

        <input value="Submit" type="submit">
    </form>

So, we need setup the name of the input as object[property] for got an object. In the above example, we got a data with the follow JSON:

{
"name": {
  "first": "some data",
  "last": "some data"
 }
}

Answer 5

you code is fine but never executed, cause of submit button [type="submit"] just replace it by type=button

<input value="Submit" type="button" onclick="submitform()">

inside your script; form is not declared.

let form = document.forms[0];
xhr.open(form.method, form.action, true);

Answer 6

Use FormData API

Capture the form data using FormData API formData= new FormData(form)
Convert it into JSON using JSON.stringify(Object.fromEntries(formData))
Send this strigified json as ajax payload

var form = document.getElementById('myForm');
form.onsubmit = function(event){
        var xhr = new XMLHttpRequest();
        var formData = new FormData(form);
        //open the request
        xhr.open('POST','http://localhost:7000/tests/v1.0/form')
        xhr.setRequestHeader("Content-Type", "application/json");

        //send the form data
        xhr.send(JSON.stringify(Object.fromEntries(formData)));

        xhr.onreadystatechange = function() {
            if (xhr.readyState == XMLHttpRequest.DONE) {
                form.reset(); //reset form after AJAX success or do something else
            }
        }
        //Fail the onsubmit to avoid page refresh.
        return false; 
    }

Taken from an article I wrote here: https://metamug.com/article/html5/ajax-form-submit.html

Answer 7

So I've got this HTML form:

<html>
<head><title>test</title></head>
<body>
    <form action="myurl" method="POST" name="myForm">
        <p><label for="first_name">First Name:</label>
        <input type="text" name="first_name" id="fname"></p>

        <p><label for="last_name">Last Name:</label>
        <input type="text" name="last_name" id="lname"></p>

        <input value="Submit" type="submit" onclick="submitform()">
    </form>
</body>
</html>

Which would be the easiest way to send this form's data as a JSON object to my server when a user clicks on submit?

UPDATE: I've gone as far as this but it doesn't seem to work:

<script type="text/javascript">
    function submitform(){
        alert("Sending Json");
        var xhr = new XMLHttpRequest();
        xhr.open(form.method, form.action, true);
        xhr.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');
        var j = {
            "first_name":"binchen",
            "last_name":"heris",
        };
        xhr.send(JSON.stringify(j));

What am I doing wrong?

Answer 8

微型库字段辅助正是这样做的： collectValues(formElement)将从输入字段返回一个规范化的 json（这也意味着，复选框作为布尔值，选择作为字符串等）。

Answer 9

If you want to use pure javascript in 2022...

const ajax = async (config) => {
    const request = await fetch(config.url, {
        method: config.method,
        headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/json'
        },
        body: JSON.stringify(config.payload)
    });
    response = await request.json();
    console.log('response', response)
    return response
}

// usage
response = ajax({
    method: 'POST',
    url: 'example.com',
    payload: {"name": "Stackoverflow"}
})

Answer 10

I found a way to pass a JSON message using only a HTML form.

This example is for GraphQL but it will work for any endpoint that is expecting a JSON message.

GrapqhQL by default expects a parameter called operations where you can add your query or mutation in JSON format. In this specific case I am invoking this query which is requesting to get allUsers and return the userId of each user.

{ 
 allUsers 
  { 
  userId 
  }
}

I am using a text input to demonstrate how to use it, but you can change it for a hidden input to hide the query from the user.

<html>
<body>
    <form method="post" action="http://localhost:8080/graphql">
        <input type="text" name="operations" value="{&quot;query&quot;: &quot;{ allUsers { userId } }&quot;, "variables":  {}}"/>
        <input type="submit" />
    </form>
</body>
</html>

In order to make this dynamic you will need JS to transport the values of the text fields to the query string before submitting your form. Anyway I found this approach very interesting. Hope it helps.

How to send a JSON object using html form data

Question

9 answers

solution1
167 ACCPTED 2014-03-05 10:35:07

solution2
65 2014-03-05 10:33:44

solution3
6 2020-08-04 21:15:00

solution4
5 2020-03-03 02:31:16

solution5
4 2019-04-05 02:57:42

solution6
3 2021-09-29 10:15:30

Use FormData API

solution7
1 2020-12-22 22:27:07

solution8
0 2020-12-08 16:30:44

solution9
0 2022-08-30 10:04:03

solution10
-2 2020-11-20 00:02:58

How to send a JSON object using html form data

Question

9 answers

solution1 167 ACCPTED 2014-03-05 10:35:07

solution2 65 2014-03-05 10:33:44

solution3 6 2020-08-04 21:15:00

solution4 5 2020-03-03 02:31:16

solution5 4 2019-04-05 02:57:42

solution6 3 2021-09-29 10:15:30

Use FormData API

solution7 1 2020-12-22 22:27:07

solution8 0 2020-12-08 16:30:44

solution9 0 2022-08-30 10:04:03

solution10 -2 2020-11-20 00:02:58

solution1
167 ACCPTED 2014-03-05 10:35:07

solution2
65 2014-03-05 10:33:44

solution3
6 2020-08-04 21:15:00

solution4
5 2020-03-03 02:31:16

solution5
4 2019-04-05 02:57:42

solution6
3 2021-09-29 10:15:30

solution7
1 2020-12-22 22:27:07

solution8
0 2020-12-08 16:30:44

solution9
0 2022-08-30 10:04:03

solution10
-2 2020-11-20 00:02:58