How can I get form data with JavaScript/jQuery?

Question

Is there a simple, one-line way to get the data of a form as it would be if it was to be submitted in the classic HTML-only way?

For example, in:

<form>
 <input type="radio" name="foo" value="1" checked="checked" />
 <input type="radio" name="foo" value="0" />
 <input name="bar" value="xxx" />
 <select name="this">
  <option value="hi" selected="selected">Hi</option>
  <option value="ho">Ho</option>
</form>

Out:

{
 "foo": "1",
 "bar": "xxx",
 "this": "hi"
}

Something like this is too simple, since it does not (correctly) include textareas, selects, radio buttons and checkboxes:

$("#form input").each(function() {
 data[theFieldName] = theFieldValue;
});

Answer 1

$("#form input, #form select, #form textarea").each(function() {
 data[theFieldName] = theFieldValue;
});

other than that, you might want to look at serialize();

Answer 2

You are all not fully correct. You cannot write:

formObj[input.name] = input.value;

Because this way if you have multiselect list - its values will be overwritten with the last one, since it's transmitted as: "param1" : "value1", "param1" : "value2".

So, correct approach is:

if (formData[input.name] === undefined) {
    formData[input.name] = input.value;
}
else {
    var inputFieldArray = $.merge([], $.isArray(formData[input.name]) ? formData[input.name] : [formData[input.name]]);
    $.merge(inputFieldArray, [input.value]);
    formData[input.name] = $.merge([], inputFieldArray);
}

Answer 3

Here is a nice vanilla JS function I wrote to extract form data as an object. It also has options for inserting additions into the object, and for clearing the form input fields.

const extractFormData = ({ form, clear, add }) => {
  return [].slice.call(form.children).filter(node => node.nodeName === 'INPUT')
  .reduce((formData, input) => {
    const value = input.value
    if (clear) { input.value = '' }
    return {
      ...formData,
      [input.name]: value
    }
  }, add)
}

Here is an example of its use with a post request:

submitGrudge(e) {
  e.preventDefault()

  const form = e.target
  const add = { id: Date.now(), forgiven: false }
  const grudge = extractFormData({ form, add, clear: true })

  // grudge = {
  //  "name": "Example name",
  //  "offense": "Example string",
  //  "date": "2017-02-16",
  //  "id": 1487877281983,
  //  "forgiven": false
  // }

  fetch('http://localhost:3001/api/grudge', {
    method: 'post',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(grudge)
  })
    .then(response => response.json())
    .then(grudges => this.setState({ grudges }))
    .catch(err => console.log('error: ', err))
}

Answer 4

I use this:

jQuery Plugin

(function($){
  $.fn.getFormData = function(){
    var data = {};
    var dataArray = $(this).serializeArray();
    for(var i=0;i<dataArray.length;i++){
      data[dataArray[i].name] = dataArray[i].value;
    }
    return data;
  }
})(jQuery);

HTML Form

<form id='myform'>
  <input name='myVar1' />
  <input name='myVar2' />
</form>

Get the Data

var myData = $("#myForm").getFormData();

Answer 5

This method should do it. It serializes the form data and then converts them to an object. Takes care of groups of checkboxes as well.

function getFormObj(formId) {
  var formParams = {};
  $('#' + formId)
    .serializeArray()
    .forEach(function(item) {
      if (formParams[item.name]) {
        formParams[item.name] = [formParams[item.name]];
        formParams[item.name].push(item.value)
      } else {
        formParams[item.name] = item.value
      }
    });
  return formParams;
}

Answer 6

$(form).serializeArray().reduce(function (obj, item) {
      if (obj[item.name]) {
           if ($.isArray(obj[item.name])) {
               obj[item.name].push(item.value);
           } else {
                var previousValue = obj[item.name];
                obj[item.name] = [previousValue, item.value];
           }
      } else {
           obj[item.name] = item.value;
      }

     return obj;
}, {});

It will fix issue:couldn't work with multiselects.