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You are here: Reference > JavaScript > client-side > HTML DOM > objects > nodes and tags > form

form object

Browser support:
Creates a container element for controls.
The form element allows users to submit data to a server. The target URL can be specified with the action property. The method property defines the way of sending.
The contents of the message submitted to the server depend on the named form controls in the form tag. Named control means an element with a non-empty name property.
Only the contents or the state of the named form controls will be sent.
The following elements are form controls: When a form is submitted, the message contains the name/value pairs belonging to the named controls in the form. The name parameter is the value of the name property of the control. The contents of the value parameter depend on the type of the control.
Push buttons (button, input:button, input:reset, input:submit) don't play an important part in the message. If a push button is named and it is in pushed state when the form is submitted, then the name and the value (the value of the value property) of the button will be sent with the form. If a push button is not in pushed state, no information is sent with the form that belongs to the button. Since only one push button can be in pushed state at any time, they don't play an important part in the message.
The reset button can be used to reset all controls to their initial values within the form. The user can send the form to the server by clicking on the submit button.
The other controls are useful for the message submitted to the server.
If you want to check the contents of a form control before submitting, register an event handler for the onsubmit event. In your event handler you can check the required fields and if some errors are found, then you can cancel the onsubmit event (see the page for the returnValue property and the preventDefault method).
Another possibility to check the contents of a form control before submitting is to use simple push buttons instead of submit buttons. In your onclick event handler method you can check the required fields and if no error was found, you can send the form with the submit method. See Example 2 for details.

Syntax:

Properties that reference the object:
•object.form
Methods that return the object:
•document.createElement ("form")
•forms.item (nameOrIndex [, subIndex])
•forms.namedItem (name)
The base interface, through which you can add new functionalities to the form object, is the HTMLFormElement interface.
If you want to see the HTML objects by categories, please visit this page.
HTML page for this element: form

Possible members:

 Properties
Methods
Events
Style properties
accept
Sets or retrieves a comma-separated list of accepted content types.
acceptCharset
Sets or retrieves a list of character encodings for a form.
accessKey
Sets or retrieves an access key to an element.
action
Sets or retrieves a form processing agent. With this property you can set an URL to call when the form is sent.
all
Represents a collection of all elements contained by an element or the entire document.
attributes
Represents a collection of attribute nodes that belong to an element.
autocomplete
Sets or retrieves whether the text field should give the user some suggestion during typing.
baseURI
10
 Returns the base URL for the object.
behaviorUrns
Represents a collection of the Uniform Resource Names for all behaviors attached to an element.
canHaveChildren
Retrieves a Boolean value that indicates whether the element can contain child elements.
canHaveHTML
Retrieves a Boolean value that indicates whether the element can contain HTML formatted text.
childElementCount
93.5
 Returns the number of element nodes that are direct descendants of the current element.
childNodes
Represents a collection of all nodes that are direct descendants of an element.
children
3.5
 Represents a collection of all element nodes that are direct descendants of an element.
className
Sets or retrieves the style class or classes that belong to the element.
clientHeight
Returns the height of the visible area for an object, in pixels. The value contains the height with the padding, but it does not include the scrollBar, border, and the margin.
clientLeft
Returns the width of the left border in pixels.
clientTop
Returns the height of the top border in pixels.
clientWidth
Returns the width of the visible area for an object, in pixels. The value contains the width with the padding, but does not include the scrollBar, border, and the margin.
contentEditable
3
 Sets or retrieves whether the contents of the object are editable.
currentStyle
Represents the computed style settings for an element.
dir
Sets or retrieves the text direction as related to the lang property.
disabled
Sets or retrieves the state of an object for user interaction.
draggable
3.55
 Sets or retrieves whether an element is draggable.
elements
Represents a collection of all form control elements in a form.
encoding
Sets or retrieves how form data should be encoded for submitting to the server.
enctype
Sets or retrieves how form data should be encoded for submitting to the server.
filters
Represents a collection of all filter objects applied to an element.
firstChild
Returns a reference to the first child of the current element.
firstElementChild
93.5
 Returns a reference to the first child element of the current element.
hideFocus
Specifies or returns whether a dotted rectangle (focus rectangle) is drawn around an object while it has focus.
id
Sets or retrieves a unique identifier for the object.
innerHTML
Sets or retrieves the inner HTML content (the source code between the opening and closing tags) of an element.
innerText
Sets or returns the text content of an element including the text content of its descendants.
isContentEditable
Returns a Boolean value that indicates whether the contents of the object are editable by the user.
isDisabled
Returns a Boolean value that indicates whether the object is disabled.
isMultiLine
Returns a Boolean value that indicates whether the contents of an element can be multiline or not.
isTextEdit
Returns a Boolean value that indicates whether the createTextRange method can be used for the element.
lang
Specifies or returns the language of the element.
language
Sets or retrieves the scripting language for the current element. Use it only for the script element.
lastChild
Returns a reference to the last child of the current element.
lastElementChild
93.5
 Returns a reference to the last child element of the current element.
length
Returns the number of form controls in a form element or the number of options in a select or keygen element.
localName
9
 Returns the local part of the qualified name of the current node.
method
Specifies or returns how the data of a form should be submitted to the server. When the user clicks on the submit button of a form, the data of the named elements in the form will be sent. The data contains the name and the value of the named element.
name
Sets or retrieves the name of an element.
namespaceURI
93.6
 Sets or returns the namespace URI of the current node.
nextElementSibling
93.5
 Returns a reference to the next child element of the current element's parent.
nextSibling
Returns a reference to the next child of the current element's parent.
nodeName
Returns the name of the current node.
nodeType
Returns an integer that indicates the type of the node.
nodeValue
Sets or returns the value of the current node.
offsetHeight
Returns the height of the visible area for an object, in pixels. The value contains the height with the padding, scrollBar, and the border, but does not include the margin.
offsetLeft
Returns the left position of an object relative to the left side of its offsetParent element, in pixels.
offsetParent
Returns a reference to the closest ancestor element in the DOM hierarchy from which the position of the current element is calculated.
offsetTop
Returns the top position of the object relative to the top side of its offsetParent element, in pixels.
offsetWidth
Returns the width of the visible area for an object, in pixels. The value contains the width with the padding, scrollBar, and the border, but does not include the margin.
outerHTML
Sets or retrieves the outer HTML content (the source code including the opening and closing tags) of an element.
outerText
Sets or returns the text content of an element including the text content of its descendants.
ownerDocument
Returns the document object that contains the current node.
parentElement
Returns the parent element of the object in the DOM hierarchy.
parentNode
Returns the parent element of the current node in the DOM hierarchy.
parentTextEdit
Returns the closest ancestor element of the current element in the DOM hierarchy that can be used to create a TextRange object.
previousElementSibling
93.5
 Returns a reference to the previous child element of the current element's parent.
previousSibling
Returns a reference to the previous node of the current element's parent.
readyState
Returns a string value that represents the state of the object.
runtimeStyle
Represents the overridden style settings for an element.
scopeName
Retrieves the local name of the namespace declared for the current element.
scrollHeight
Returns the total height of an element's contents, in pixels. The value contains the height with the padding, but does not include the scrollBar, border, and the margin.
scrollLeft
Sets or retrieves the number of pixels by which the contents of an object are scrolled to the left.
scrollTop
Sets or retrieves the number of pixels by which the contents of an object are scrolled upward.
scrollWidth
Returns the total width of an element's contents, in pixels. The value contains the width with the padding, but does not include the scrollBar, border, and the margin.
sourceIndex
Returns the position of the current object in the all collection of the document.
spellcheck
Sets or retrieves whether the automatic spellchecker is enabled.
style
Represents the inline style settings for an element or a CSS rule.
tabIndex
Specifies or returns the tabbing order for keyboard navigation using the TAB key.
tagName
Returns the tag name of the current element.
tagUrn
Sets or retrieves the Uniform Resource Name (URN) of the namespace declared for the current element.
target
Specifies or returns the target window or frame where the document is to be opened.
textContent
9
 Sets or returns the text content of an element including the text content of its descendants.
title
Specifies or returns a tooltip for an element.
uniqueID
Returns the unique identifier generated by the browser for the object.
unselectable
Sets or retrieves whether the selection process can start in an element's content.

Example HTML code 1:

This example illustrates the use of the form element:
 
<form action="#URL#" method="post">
    User Name: <input type="text" name="userName" />
    <br />
    Password: <input type="password" name="password" />
    <br />
    <input type="reset" value="Reset" />
    <input type="submit" value="Sign in" />
</form>
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Example HTML code 2:

This example checks the state of some elements before submitting the form:
 
<head>
    <script type="text/javascript">
        function CheckAndSubmit () {
            var userName = document.getElementById ("userName");
            if (userName.value.length < 3) {
                alert ("The name of the user must be at least 3 characters long!");
                return;
            }

            var password = document.getElementById ("password");
            var repassword = document.getElementById ("repassword");
            if (password.value.length < 6) {
                alert ("The password must be at least 6 characters long!");
                return;
            }
            if (repassword.value != password.value) {
                alert ("The two passwords are different!");
                return;
            }

            var acceptAgreement = document.getElementById ("acceptAgreement");
            if (!acceptAgreement.checked) {
                alert ("You must accept the User Agreement to register!");
                return;
            }

            var regForm = document.getElementById ("regForm");
            regForm.submit ();
        }
    </script>
</head>
<body>
    <form id="regForm" method="post" action="#URL#">
        User Name: <input type="text" name="userName" id="userName" />
        <br />
        Password: <input type="password" name="password" id="password" />
        <br />
        Repeat Password: <input type="password" name="repassword" id="repassword" />
        <br /><br />
        <input type="checkbox" name="acceptAgreement" id="acceptAgreement" /> 
        <label for="acceptAgreement">I accept the User Agreement and Privacy Policy</label>
        <br /><br />
        <input type="button" value="Register" onclick="CheckAndSubmit ()" />
    </form>
</body>
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Example HTML code 3:

This example and the next one use AJAX to submit a form without reloading the page. The two examples are similar, but the first one uses synchronous while the second one uses asynchronous data transfer. In synchronous mode, the send method of the XMLHttpRequest object waits for a reply, so the user cannot interact with the browser until the response has completed. In asynchronous mode, the send method does not wait for a reply but instead returns immediately, so it allows you to perform other operations while a time-consuming task is being performed in the background.
 Code
ajax_form.js
register.php 
<head>
    <script type="text/javascript" src="ajax_form.js"></script>
    <style>
        .error {
            display: none;
            color: #a00000;
            font-weight: bold;
        }
    </style>
    <script type="text/javascript">     
        function HideAllErrorFields () {
            for (var i = 1; i <= 4; i++) {
                var field = document.getElementById ("error" + i);
                field.style.display = "none";
            }
        }

        function ShowErrorFields (idsStr) {
            var ids = idsStr.split (",");
            for (var i = 0; i < ids.length; i++) {
                var field = document.getElementById ("error" + ids[i]);
                if (field) {
                    field.style.display = "block";
                }
            }
        }

        function AjaxSend (form, url, method) {
                // hide all error fields
            HideAllErrorFields ();
            
                // get message data
            var data = GetMessageBody (form);   // defined in ajax_form.js

                // send the request
            var httpRequest = CreateRequestObj ();  // defined in ajax_form.js
                // try..catch is required if working offline
            try {
                httpRequest.open (method, url, false);  // synchron
                httpRequest.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
                httpRequest.send (data);
            }
            catch (e) {
                alert ("Cannot connect to the server!");
                return;
            }

                // handle the response
            if (IsRequestSuccessful (httpRequest)) {    // defined in ajax_form.js
                if (httpRequest.responseText === "ok") {    // registration is successful
                    alert ("Thank you for registering");
                    /*
                        // if redirection is required
                    location.href = "/index.php";
                    */
                }
                else {  // some fields are invalid
                    ShowErrorFields (httpRequest.responseText);
                }
            }
            else {
                alert ("An error occurred while registering. Please try it again.");
            }
        }
    </script>
</head>
<body>
    This is a sample registration form.
    The username must be between 2 and 20 characters, the password must be between 6 and 20 characters.
    A user named Dottoro is already registered.
    <br />
    Try to register both valid and invalid values!
    <br /><br />
    <form onsubmit="AjaxSend (this, 'register.php', 'post'); return false;">
        User Name: <input type="text" name="userName" />
        <div class="error" id="error1">Must be between 2 and 20 characters.</div>
        <div class="error" id="error2">A user already exists with the same name.</div>
        <br /><br />
        Password: <input type="password" name="password" />
        <div class="error" id="error3">Must be between 6 and 20 characters.</div>
        <br /><br />
        Repeat Password: <input type="password" name="repassword" />
        <div class="error" id="error4">Must be the same as the password.</div>
        <br /><br />
        <input type="submit" value="Register" />
    </form>
</body>
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Example HTML code 4:

This example is similar to the previous one, but it uses asynchronous data transfer and displays blinking text while waiting for the server response (the register_delay.php script waits two seconds before responding).
 Code
ajax_form.js
register_delay.php 
<head>
    <script type="text/javascript" src="ajax_form.js"></script>
    <style>
        .error {
            display: none;
            color: #a00000;
            font-weight: bold;
        }
        #progress {
            visibility: hidden;
            color: #00a000;
        }
    </style>
    <script type="text/javascript">     
        function HideAllErrorFields () {
            for (var i = 1; i <= 4; i++) {
                var field = document.getElementById ("error" + i);
                field.style.display = "none";
            }
        }

        function ShowErrorFields (idsStr) {
            var ids = idsStr.split (",");
            for (var i = 0; i < ids.length; i++) {
                var field = document.getElementById ("error" + ids[i]);
                if (field) {
                    field.style.display = "block";
                }
            }
        }

        var registering = false;
        
        function OnReadyStateChanged (httpRequest, form) {
            if (httpRequest.readyState == 0 || httpRequest.readyState == 4) {
                
                registering = false;
                StopAnim ();
                
                    // prevent memory leaks
                httpRequest.onreadystatechange = null;
                
                if (IsRequestSuccessful (httpRequest)) {    // defined in ajax_form.js
                    if (httpRequest.responseText === "ok") {    // registration is successful
                        alert ("Thank you for registering");
                        /*
                            // if redirection is required
                        location.href = "/index.php";
                        */
                    }
                    else {  // some fields are invalid
                        ShowErrorFields (httpRequest.responseText);
                    }
                }
                else {
                    alert ("An error occurred while registering. Please try it again.");
                }
            }
        }

        function AjaxSend (form, url, method) {
                // avoid resend data while registering
            if (registering) {
                return;
            }
                // hide all error fields
            HideAllErrorFields ();
            
                // get message data
            var data = GetMessageBody (form);   // defined in ajax_form.js

                // send the request
            var httpRequest = CreateRequestObj ();  // defined in ajax_form.js
                // try..catch is required if working offline
            try {
                httpRequest.open (method, url, true);   // asynchron
                httpRequest.onreadystatechange = function () {OnReadyStateChanged (httpRequest, form)};
                httpRequest.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
                httpRequest.send (data);
            }
            catch (e) {
                alert ("Cannot connect to the server!");
                return;
            }

            registering = true;
            StartAnim ();
        }

            // blinking text
        var animTimerId = 0;
        function StartAnim () {
            var progress = document.getElementById ("progress");
            progress.style.visibility = "visible";
            animTimerId = setInterval (RegAnim, 100);
        }
        function RegAnim () {
            var progress = document.getElementById ("progress");
            progress.style.visibility = (progress.style.visibility == "visible") ? "hidden" : "visible";
        }
        function StopAnim () {
            var progress = document.getElementById ("progress");
            progress.style.visibility = "hidden";
            clearInterval (animTimerId);
        }

    </script>
</head>
<body>
    This is a sample registration form.
    The username must be between 2 and 20 characters, the password must be between 6 and 20 characters.
    A user named Dottoro is already registered.
    <br />
    Try to register both valid and invalid values!
    <br /><br />
    <form onsubmit="AjaxSend (this, 'register_delay.php', 'post'); return false;">
        User Name: <input type="text" name="userName" />
        <div class="error" id="error1">Must be between 2 and 20 characters.</div>
        <div class="error" id="error2">A user already exists with the same name.</div>
        <br /><br />
        Password: <input type="password" name="password" />
        <div class="error" id="error3">Must be between 6 and 20 characters.</div>
        <br /><br />
        Repeat Password: <input type="password" name="repassword" />
        <div class="error" id="error4">Must be the same as the password.</div>
        <br /><br />
        <input type="submit" value="Register" />
        <div id="progress">Registering</div>
    </form>
</body>
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Related pages:

button
fieldset
input:button
input:checkbox
input:file
input:hidden
input:image
input:password
input:radio
input:range
input:reset
input:search
input:submit
input:text
label
legend
optgroup
option
select
textarea

External links:

form element (MSDN)
form element (Safari Reference Library)
form element (W3C)
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