JavaScript - Getting HTML form values

142
votes

How can I get the value of an HTML form to pass to JavaScript?

Is this correct? My script takes two arguments one from textbox, one from the dropdown box.

<body>
<form name="valform" action="" method="POST">

Credit Card Validation: <input type="text" id="cctextboxid" name="cctextbox"><br/>
Card Type: <select name="cardtype" id="cardtypeid">
  <option value="visa">Visa</option>
  <option value="mastercard">MasterCard</option>
  <option value="discover">Discover</option>
  <option value="amex">Amex</option>
  <option value="diners">Diners Club</option>
</select><br/>
<input type="button" name="submit" value="Verify Credit Card" onclick="isValidCreditCard(document.getElementById('cctextboxid').value,document.getElementById('cardtypeid').value)" />
</body>
15
javascripthtml
What do you mean by "value of a form in HTML code" exactly? - Pekka
question is quite clear - laurentngu
@laurentngu the question is does he mean "a value of an HTML form", meaning one value out of the many values, or does he mean the "value of the entire HTML form", meaning all of the values in one big "serialized" value - bluejayke
The question is clear... but clearly it doesn't make a lot of sense to pass the value of a form. - Matthew

15 Answers

138
votes

HTML:

<input type="text" name="name" id="uniqueID" value="value" />

JS:

var nameValue = document.getElementById("uniqueID").value;
90
votes

If you want to retrieve the form values (such as those that would be sent using an HTTP POST) you can use:

JavaScript

const formData = new FormData(document.querySelector('form'))
for (var pair of formData.entries()) {
  // console.log(pair[0] + ': ' + pair[1]);
}

form-serialize (https://code.google.com/archive/p/form-serialize/)

serialize(document.forms[0]);

jQuery

$("form").serializeArray()
43
votes

Here is an example from W3Schools:

function myFunction() {
    var elements = document.getElementById("myForm").elements;
    var obj ={};
    for(var i = 0 ; i < elements.length ; i++){
        var item = elements.item(i);
        obj[item.name] = item.value;
    }

    document.getElementById("demo").innerHTML = JSON.stringify(obj);
}

The demo can be found here.

29
votes

document.forms will contain an array of forms on your page. You can loop through these forms to find the specific form you desire.

var form = false;
var length = document.forms.length;
for(var i = 0; i < length; i++) {
    if(form.id == "wanted_id") {
        form = document.forms[i];
    }
}

Each form has an elements array which you can then loop through to find the data that you want. You should also be able to access them by name

var wanted_value = form.someFieldName.value;
jsFunction(wanted_value);
12
votes

My 5 cents here, using form.elements which allows you to query each field by it's name, not only by iteration:

const form = document.querySelector('form[name="valform"]');
const ccValidation = form.elements['cctextbox'].value;
const ccType = form.elements['cardtype'].value;
11
votes

This is a developed example of https://stackoverflow.com/a/41262933/2464828

Consider

<form method="POST" enctype="multipart/form-data" onsubmit="return check(event)">
    <input name="formula">
</form>

Let us assume we want to retrieve the input of name formula. This can be done by passing the event in the onsubmit field. We can then use FormData to retrieve the values of this exact form by referencing the SubmitEvent object.

const check = (e) => {
    const form = new FormData(e.target);
    const formula = form.get("formula");
    console.log(formula);
    return false
};

The JavaScript code above will then print the value of the input to the console.

If you want to iterate the values, i.e., get all the values, then see https://developer.mozilla.org/en-US/docs/Web/API/FormData#Methods

11
votes

I found this the most elegant solution.

function handleSubmit(e) {
  e.preventDefault();
  const formData = new FormData(e.target);
  const formProps = Object.fromEntries(formData);
}
3
votes

Expanding on Atrur Klesun's idea... you can just access it by its name if you use getElementById to reach the form. In one line:

document.getElementById('form_id').elements['select_name'].value;

I used it like so for radio buttons and worked fine. I guess it's the same here.

2
votes

Several easy-to-use form serializers with good documentation.

In order of Github stars,

  1. jquery.serializeJSON

  2. jquery-serialize-object

  3. form2js

  4. form-serialize

2
votes

Please try to change the code as below:

<form
   onSubmit={e => {
     e.preventDefault();
     e.stopPropagation();

     const elements = Array.from(e.currentTarget) as HTMLInputElement[];

     const state = elements.reduce((acc, el) => {
       if (el.name) {
         acc[el.name] = el.value;
       }

       return acc;
     }, {});

     console.log(state); // {test: '123'}
   }}
>
   <input name='test' value='123' />
</form>
1
votes

Quick solution to serialize a form without any libraries

function serializeIt(form) {
  return (
    Array.apply(0, form.elements).map(x => 
      (
        (obj => 
          (
            x.type == "radio" ||
            x.type == "checkbox"
          ) ?
            x.checked ? 
              obj
            : 
              null
          :
            obj
        )(
          {
            [x.name]:x.value
          }
        )
      )
    ).filter(x => x)
  );
}

function whenSubmitted(e) {
  e.preventDefault()
  console.log(
    JSON.stringify(
      serializeIt(document.forms[0]),
      4, 4, 4
    )
  )
}
<form onsubmit="whenSubmitted(event)">
<input type=text name=hiThere value=nothing>
<input type=radio name=okRadioHere value=nothin>
<input type=radio name=okRadioHere1 value=nothinElse>
<input type=radio name=okRadioHere2 value=nothinStill>

<input type=checkbox name=justAcheckBox value=checkin>
<input type=checkbox name=justAcheckBox1 value=checkin1>
<input type=checkbox name=justAcheckBox2 value=checkin2>

<select name=selectingSomething>
<option value="hiThere">Hi</option>
<option value="hiThere1">Hi1</option>
<option value="hiThere2">Hi2</option>
<option value="hiThere3">Hi3</option>
</select>
<input type=submit value="click me!" name=subd>
</form>
1
votes

This is the answer of your question.

You can pass the values of the form fields to the function by using this.<<name of the field>>.value.

And also changed input submit to button submit. Called the function from form.

<body>
   <form name="valform" method="POST" onsubmit="isValidCreditCard(this.cctextbox.value, this.cardtype.value)">
   Credit Card Validation: <input type="text" id="cctextboxid" name="cctextbox"><br/>
   Card Type: 
   <select name="cardtype" id="cardtypeid">
      ...
   </select>
   <br/>
   <button type="submit">Verify Credit Card</button>
</body>

Technically you can do it in your function by using document.getElementById("cctextboxid"). But his solution is concise and simple code.

1
votes
<form id='form'>
    <input type='text' name='title'>
    <input type='text' name='text'>
    <input type='email' name='email'>
</form>

const element = document.getElementByID('#form')
const data = new FormData(element)
const form = Array.from(data.entries())
/*
form = [
    ["title", "a"]
    ["text", "b"]
    ["email", "c"]
]
*/
for (const [name, value] of form) {
    console.log({ name, value })
    /*
    {name: "title", value: "a"}
    {name: "text", value: "b"}
    {name: "email", value: "c"}
    */
}
0
votes

I know this is an old post but maybe someone down the line can use this.

// use document.form["form-name"] to reference the form
const ccForm = document.forms["ccform"];

// bind the onsubmit property to a function to do some logic
ccForm.onsubmit = function(e) {

  // access the desired input through the var we setup
  let ccSelection = ccForm.ccselect.value;
  console.log(ccSelection);

  e.preventDefault();
}
<form name="ccform">
  <select name="ccselect">
    <option value="card1">Card 1</option>
    <option value="card2">Card 2</option>
    <option value="card3">Card 3</option>
  </select>
  <button type="submit">Enter</button>
</form>
-1
votes
<input type="text" id="note_text" />

let value = document.getElementById("note_text").value;