form serialize javascript (no framework)

Question

Wondering is there a function in javascript without jquery or any framework that allows me to serialize the form and access the serialized version?

Answer 1

I refactored TibTibs answer into something that's much clearer to read. It is a bit longer because of the 80 character width and a few comments.

Additionally, it ignores blank field names and blank values.

// Serialize the specified form into a query string.
//
// Returns a blank string if +form+ is not actually a form element.
function $serialize(form, evt) {
  if(typeof(form) !== 'object' && form.nodeName !== "FORM")
    return '';

  var evt    = evt || window.event || { target: null };
  evt.target = evt.target || evt.srcElement || null;
  var field, query = '';

  // Transform a form field into a query-string-friendly
  // serialized form.
  //
  // [NOTE]: Replaces blank spaces from its standard '%20' representation
  //         into the non-standard (though widely used) '+'.
  var encode = function(field, name) {
    if (field.disabled) return '';

    return '&' + (name || field.name) + '=' +
           encodeURIComponent(field.value).replace(/%20/g,'+');
  }

  // Fields without names can't be serialized.
  var hasName = function(el) {
    return (el.name && el.name.length > 0)
  }

  // Ignore the usual suspects: file inputs, reset buttons,
  // buttons that did not submit the form and unchecked
  // radio buttons and checkboxes.
  var ignorableField = function(el, evt) {
    return ((el.type == 'file' || el.type == 'reset')
        || ((el.type == 'submit' || el.type == 'button') && evt.target != el)
        || ((el.type == 'checkbox' || el.type == 'radio') && !el.checked))
  }

  var parseMultiSelect = function(field) {
    var q = '';

    for (var j=field.options.length-1; j>=0; j--) {
      if (field.options[j].selected) {
        q += encode(field.options[j], field.name);
      }
    }

    return q;
  };

  for(i = form.elements.length - 1; i >= 0; i--) {
    field = form.elements[i];

    if (!hasName(field) || field.value == '' || ignorableField(field, evt))
      continue;

    query += (field.type == 'select-multiple') ? parseMultiSelect(field)
                                               : encode(field);
  }

  return (query.length == 0) ? '' : query.substr(1);
}

Answer 2

This could be done by very simple function as follows

function serialize(form) {
        let requestArray = [];
        form.querySelectorAll('[name]').forEach((elem) => {
            requestArray.push(elem.name + '=' + elem.value);
        });
        if(requestArray.length > 0)
            return requestArray.join('&');
        else
            return false;
    }

 serialized = serialize(document.querySelector('form'))
  console.log(serialized);

<form>

  <input type='text' name='fname' value='Johne'/>
  <input type='text' name='lname' value='Doe'/>
  <input type='text' name='contact[]' value='99999999'/>
  <input type='text' name='contact[]' value='34423434345'/>

</form>

Answer 3

I've grabbed the entries() method of formData from @moison answer and from MDN it's said that :

The FormData.entries() method returns an iterator allowing to go through all key/value pairs contained in this object. The key of each pair is a USVString object; the value either a USVString, or a Blob.

but the only issue is that mobile browser (android and safari are not supported ) and IE and Safari desktop too

but basically here is my approach :

let theForm =  document.getElementById("contact"); 

theForm.onsubmit = function(event) {
    event.preventDefault();

    let rawData = new FormData(theForm);
    let data = {};

   for(let pair of rawData.entries()) {
     data[pair[0]] = pair[1]; 
    }
    let contactData = JSON.stringify(data);
    console.warn(contactData);
    //here you can send a post request with content-type :'application.json'

};

the code can be found here

Answer 4

Improving upon David Lemon's answer.

This converts form data to JSON and allows you to set the form from a data object.

const main = () => {
  const form = document.forms['info'];
  const data = {
    "user_name"       : "John",
    "user_email"      : "john@jonhson.com",
    "user_created"    : "2020-03-24",
    "user_age"        : 42,
    "user_subscribed" : true,
    "user_interests"  : "sports",
    "user_message"    : "Hello My Friend"
  };

  populateForm(form, data);
  updateJsonView(form);
  form.addEventListener('change', (e) => updateJsonView(form));
}

const getFieldValue = (field, opts) => {
  let type = field.getAttribute('type');
  if (type) {
    switch (type) {
      case 'checkbox':
        return field.checked;
      case 'number':
        return field.value.includes('.')
          ? parseFloat(field.value)
          : parseInt(field.value, 10);
    }
  }
  if (opts && opts[field.name] && opts[field.name].type) {
    switch (opts[field.name].type) {
      case 'int':
        return parseInt(field.value, 10);
      case 'float':
        return parseFloat(field.value);
    }
  }
  return field.value;
}

const setFieldValue = (field, value) => {
  let type = field.getAttribute('type');
  if (type) {
    switch (type) {
      case 'checkbox':
        field.checked = value;
        break;
      default:
        field.value = value;
        break;
    }
  } else {
    field.value = value;
  }
}

const extractFormData = (form, opts) => {
  return Array.from(form.elements).reduce((data, element) => {
    return Object.assign(data, { [element.name] : getFieldValue(element, opts) });
  }, {});
};

const populateForm = (form, data) => {
  return Array.from(form.elements).forEach((element) => {
    setFieldValue(element, data[element.name]);
  });
};

const updateJsonView = (form) => {
  let fieldOptions = {};
  let formData = extractFormData(form, fieldOptions);
  let serializedData = JSON.stringify(formData, null, 2);
  document.querySelector('.json-view').textContent = serializedData;
};

main();

.form-field {
  margin-bottom: 0.5em;
}

.form-field label {
  display: inline-block;
  font-weight: bold;
  width: 7em;
  vertical-align: top;
}

.json-view {
  position: absolute;
  top: 0.667em;
  right: 0.667em;
  border: thin solid grey;
  padding: 0.5em;
  white-space: pre;
  font-family: monospace;
  overflow: scroll-y;
  max-height: 100%;
}

<form name="info" action="/my-handling-form-page" method="post">
  <div class="form-field">
    <label for="name">Name:</label>
    <input type="text" id="name" name="user_name">
  </div>
  <div class="form-field">
    <label for="mail">E-mail:</label>
    <input type="email" id="mail" name="user_email">
  </div>
  <div class="form-field">
    <label for="created">Date of Birth:</label>
    <input type="date" id="created" name="user_created">
  </div>
  <div class="form-field">
    <label for="age">Age:</label>
    <input type="number" id="age" name="user_age">
  </div>
  <div class="form-field">
    <label for="subscribe">Subscribe:</label>
    <input type="checkbox" id="subscribe" name="user_subscribed">
  </div>
  <div class="form-field">
    <label for="interests">Interest:</label>
    <select required=""  id="interests" name="user_interests">
      <option value="" selected="selected">- None -</option>
      <option value="drums">Drums</option>
      <option value="js">Javascript</option>
      <option value="sports">Sports</option>
      <option value="trekking">Trekking</option>
    </select>
  </div>
  <div class="form-field">
    <label for="msg">Message:</label>
    <textarea id="msg" name="user_message"></textarea>
  </div>
</form>
<div class="json-view"></div>

Answer 5

  // supports IE8 and IE9 
  function serialize(form) {
    var inputs = form.elements;
    var array = [];
    for(i=0; i < inputs.length; i++) {
      var inputNameValue = inputs[i].name + '=' + inputs[i].value;
      array.push(inputNameValue);
    }
    return array.join('&');
  }
 //using the serialize function written above
 var form = document.getElementById("form");//get the id of your form. i am assuming the id to be named form.
 var form_data = serialize(form);
 var xhr = new XMLHttpRequest();
 xhr.send(form_data);

 //does not work with IE8 AND IE9
 var form = document.querySelector('form');
 var data = new FormData(form);
 var xhr = new XMLHttpRequest();
 xhr.send(data);

Answer 6

Using JavaScript reduce function should do a trick for all browsers, including IE9 >:

Array.prototype.slice.call(form.elements) // convert form elements to array
    .reduce(function(acc,cur){   // reduce 
        var o = {type : cur.type, name : cur.name, value : cur.value}; // get needed keys
        if(['checkbox','radio'].indexOf(cur.type) !==-1){
            o.checked = cur.checked;
        } else if(cur.type === 'select-multiple'){
            o.value=[];
            for(i=0;i<cur.length;i++){
                o.value.push({
                    value : cur.options[i].value,
                    selected : cur.options[i].selected
                });
            }
        }
        acc.push(o);
        return acc;
 },[]);

Live example bellow.

var _formId = document.getElementById('formId'),
    formData = Array.prototype.slice.call(_formId.elements).reduce(function(acc,cur,indx,arr){
        var i,o = {type : cur.type, name : cur.name, value : cur.value};
        if(['checkbox','radio'].indexOf(cur.type) !==-1){
            o.checked = cur.checked;
        } else if(cur.type === 'select-multiple'){
            o.value=[];
            for(i=0;i<cur.length;i++){
                o.value.push({
                    value : cur.options[i].value,
                    selected : cur.options[i].selected
                });
            }
        }
        acc.push(o);
        return acc;
    },[]);

// view
document.getElementById('formOutput').innerHTML = JSON.stringify(formData, null, 4);

<form id="formId">
    <input type="text" name="texttype" value="some text">
    <select>
        <option value="Opt 1">Opt 1</option>
        <option value="Opt 2" selected>Opt 2</option>
        <option value="Opt 3">Opt 3</option>
    </select>
    <input type="checkbox" name="checkboxtype" value="Checkbox 1" checked> Checkbox 1
    <input type="checkbox" name="checkboxtype" value="Checkbox 2"> Checkbox 2
    <input type="radio" name="radiotype" value="Radio Btn 1"> Radio Btn 1
    <input type="radio" name="radiotype" value="Radio Btn 2" checked> Radio Btn 2
    <select multiple>
        <option value="Multi 1" selected>Multi 1</option>
        <option value="Multi 2">Saab</option>
        <option value="Multi 3" selected>Multi 3</option>
    </select>
</form>
<pre><code id="formOutput"></code></pre>