Html session 10:
Introduction :
HTML, the core language of the World Wide Web is being used for designing Web pages for nearly a decade. With the continuous evolvement in the Web, Web designers and programmers find it difficult to make pages more flexible and dynamic in behavior. The dynamic behavior is particularly expected when displaying Web forms to the users. For example, HTML5 allows creating combo boxes, adding placeholder text on the page, providing client-side validations through JavaScript, and achieving dynamic behavior using Document Object Model (DOM) API.
Although Internet Explorer 9 and Google Chrome 19 support most HTML5 features, there are some that are supported only in Opera 11.
Introduction to HTML5 Forms
Among the other features of HTML5, there has been a great enhancement to Web forms. HTML5 Web forms are those sections on the Web page that contain special elements called as controls. The controls, such as check boxes, radio buttons, and text boxes provide a visual interface to the user to interact with them. A user provides data through these controls that is sent to the server for further processing. Thus, it is very important to create forms with lot of consideration for usability and accessibility by the users.
In HTML5, creation of form is made easier for Web developers by standardizing them with rich form controls. It also provides client-side validations that are now handled natively by the browsers. This not only reduces the load time of the pages, but also removes the need of the repetitive JavaScript codes to be included on the page.
Even the visual appearance of the forms is improved when displayed on different devices, such as iPhone, ipad, touch screens, and browsers. This enhances the users experience while interacting with them.
10.3 New Features in HTML5 Forms
HTML5 Web forms bring great improvements related to form creation for the Web developers and also for users interacting with them. The following are the changes introduced in HTML5 forms:
New form elements
New input types
New attributes
Browser-based validation
New Elements
HTML5 has introduced a range of new elements that are expanding the options for more number of elements related to input on the forms.
Table 10.1 lists the new elements in HTML5.
Element Description
progress Represents the completion progress of a task on the page
meter Represents a scale of known range
datalist Represents a set of options used with list attribute to make a drop-down control
output Represents the result of a calculation
New Input Types
The input element is a data field that allows the user to edit the data on the form. It has an attribute named type which controls the data type and characteristics of the input element.
Table 10.2 lists the new input types supported by HTML5 that specify the kind of input expected from the users on the Web page.
Type Description
email Represents the completion progress of a task on the page
search Represents a scale of known range
url Represents a set of options used with list attribute to make a drop-down control
tel Represents the result of a calculation
number Represents a numeric value in the input field
range Represents a numeric value to be selected from a range of numbers
date Represents a calendar which is shown at every click on the field
week Represents date in year-week format
Type Description
month Represents a value with year-month format
time Represents a value in hours and minutes format
datetime Represents a full date and time input field with a time zone
datetime-local Represents a full date and time with no time zone
color Represents a predefined interface for selecting color
New Attributes
HTML5 has introduced several new attributes that can be used with form and input elements. Attributes help the elements to perform their tasks.
Table 10.3 lists the new attributes in HTML5.
Table 10.3 lists the new attributes in HTML5.
Type Description
placeholder Represents a hint that help users to enter the correct data in the field
required A Boolean attribute that validates the entry in the field
multiple A Boolean attribute that allows multiple values to be entered in the field
autofocus Focuses the input element on page load
pattern Represents a regular expression for validating the field’s value
form Allows the elements to reference the form by including the form name
Browser-based Validation
HTML4 supported the use of custom JavaScript or libraries to perform validation on the client-side browsers. These validations ensure that the input fields are checked before the form is submitted to the server for further processing.
The new attributes in HTML5, such as required and pattern can be used with the input elements to perform validation. This relieves the Web developers from writing the custom JavaScript code for performing client-side validation on the Web pages. HTML5 also provides advanced validation techniques that can be used with JavaScript to set custom validation rules and messages for the input elements.
CSS Styling Techniques
A Web developer can enhance the form elements with the pseudo-class selectors, such as :required, :valid, and :invalid.
For example, the input fields which cannot be left blank while submitting the form can be displayed with an outline. To achieve this, input field with required attribute can be styled using CSS. Applying CSS styles make it easier for user to navigate and complete the form.
Code Snippet 1 shows the CSS code for formatting non-empty and incorrect data input in the input element fields on the form.
Code Snippet 1:
<style>
input:required {
outline: 1px red solid;
color: green ;
}
input:required:valid {
background-size:10px 10px;
background-position: right top;
background-repeat: no-repeat;
}
input:required:invalid {
background-size:10px 10px;
background-position: right top;
background-repeat: no-repeat;
}
</style>
</head>
<body>
<form method=”get” action=”try.php”>
Name: <input type=”text” name=”name” required=”true” /><br/>
Email: <input type=”email” name=”emailid” required=”true” />
<input type=”submit” value=”submit” />
</form>
Forms API
HTML5 has introduced JavaScript API for forms. This API is used to customize validations and processing performed on the forms. The new form’s API provides new methods, events, and properties to perform complex validations combining fields or calculations.
Table 10.4 lists the events and methods.
Events and Methods Description
setCustomValidity (message) Sets the custom error message that is displayed when the form is submitted by the user
checkValidity() Checks the validity of the e-mail address entered by the user
oninvalid Allows script to run only when the element is invalid
onforminput Allows script to run when the form gets an input from the user
onformchange Represents a regular expression for validating the field’s value
form Allows script to run when the form changes
Working with New Input Types
The type attribute of the input element determines what kind of input will be displayed on the user’s browser. The default input is type=”text”.
The registration form in the session is using the following input types:
text
label
radio
textarea
checkbox
submit
HTML5 has introduced more data-specific user interface elements. Now, you will see the new input types in detail.
E-mail Addresses
The type=”email” is used for specifying one or more e-mail addresses. To allow multiple addresses in the e-mail field, separate each address with comma-separator.
In the registration form, the input type is changed from text to email as shown in Code Snippet 2.
Code Snippet 2:
<form method=”get” action=”test.html”>
<label for=”emailid”>Email:</label>
<input type=”email” value=”” id=”emailid” name=”emailaddress”
maxlength=”255” />
<input type=”submit” value=”submit”/>
</form>
In the code, <label> tag defines a label for the element on the form. The for attribute of <label> tag binds it with the related element, that is email element, on the form. The value of for attribute must match with the value of id attribute assigned to the element.
Also, the email contains two attributes, namely id and name. The id attribute specifies a unique id for the element. The value of the id attribute should be unique within the document. It can be used as a reference for styles in style sheet or to access elements using DOM API in JavaScript.
The name attribute specifies a name for the input element. It can be used for referencing the elements in a JavaScript or form data after a form is submitted to the server for processing. The look of the input is still like a plain text field, but changes are applied behind the scenes. Browsers, such as Firefox, Chrome, and Opera will display a default error message if user submits the form with some unrecognizable contents.
Telephone Number
The type=”tel” input element is used for accepting telephone numbers. As compared to email and url types, the tel type does not impose a particular pattern. It supports characters, numbers, and special characters except new lines or carriage returns. The reason for not imposing any pattern for tel type is that different countries support various lengths and punctuation in the phone numbers. Thus, there cannot be a standard format for them.
A user can enforce a pattern for tel input type by using placeholder or pattern attribute. A JavaScript code can also be provided for performing client-side validation on the tel input type.
Code snippet 4 shows the code for including tel input type on the registration form.
Code Snippet 4:
<label for=”telno”>Telephone Number:</label>
<input type=”tel” value=”” id=”telno” name=”telephone_no”
maxlength=”10” />
Number
The input type=”number” is used for accepting only number values. The input element displayed for number type is a spinner box. The user can either type a number or click the up or down arrow to select a number in the spinner box.
Code Snippet 5:
<label for=”stud_age”>Age:</label>
<input type=”number” value=”15” id=”stud_age”
name=”studentage” min=”15” max=”45” step=”1” />
<input type=”submit” value=”submit”/>
In the code, the number input type has attributes, such as min and max to specify the minimum and maximum value for the input.
Range
The input type=”range” is similar to number type and displays a slider control on the page. The range type is used when the exact value is not required in the input. In other words, the value from this type is not accurate. For example, an online survey form asking the clients to rate the products may not receive exact values in the ratings.
Code Snippet 6 shows the code for including range input type with attributes min and max.
Code Snippet 6:
<label>Survey for packages offered[scale: 1-10]:</label>
<input type=”range” name=”rating” min=”1” max=”10” />
<input type=”submit” value=”submit”/>
In the code, the range input type contains attributes, such as min, max, step, and value. The min and max attributes are used to specify the minimum and maximum value allowed for a range and are set to 1 and 10 respectively. The step attribute specify the intervals for incrementing the value. The value of step attribute is 1 by default. The value attribute specifies the default value for the range. The default value is the midpoint of the range specified.
Date and Time
HTML5 has introduced several new input types for date and time. The format for all these date and time types is according to the ISO standards. At present only Opera provides the support for date element by displaying a calendar control.
Date
This input type contains only date in year, month, and day format. The time part is not support by date type.
Code Snippet 7 shows the code of the date input type.
Code Snippet 7:
<label for=”stdate”>Date:</label>
<input type=”date” id=”stdate” name=”startdate”
min=”2000-01-01”/>
<input type=”submit” value=”Submit” id=”btnSubmit”></input>
In the code, all date input types have min and max attributes to set the range for the dates. The default value for date input type is based on the browsers. Different browsers take different dates as default. Thus, it is advisable to set the minimum and maximum value for the date type.
<label for=”stmonth”>Month:</label>
<input type=”month” id=”stmonth” name=”startmonth” />
<input type=”submit” value=”submit”/>
In the code, all date input types have min and max attributes to set the range for the dates. The default value for date input type is based on the browsers. Different browsers take different dates as default. Thus, it is advisable to set the minimum and maximum value for the date type.
Html session 10 theory :
Color :
HTML5 provides a predefined interface for selecting the colors using input type=”color”. The input value from the color input field is a hexadecimal number. For example, #00FF00 represents a hexadecimal RGB color value.
At present, the color input type is supported on Opera browser and some new smart phones.
Code Snippet 12 shows the usage of color input type to display a color picker on the Web page.
Code Snippet :
<label>Color:</label>
<input type=”color” name=”mycolor” />
<input type=”submit” value=”submit”/>
New Form Attributes
Earlier, Web developers needed to write JavaScript snippets for performing the validations on the data entered by the users in form fields. HTML5 has provided several new attributes that perform the validations without writing JavaScript snippets for them. These attributes perform the following tasks:
Check data provided by users with the regular expression pattern assigned to the fields
Inform users with appropriate errors
Check that the required fields are not left empty by the users
Enable multiple values for the fields, if provided
These attributes can be used to support scripting drawbacks, without actually hard coding them in the Web pages. Browsers that do not understand these new attributes will ignore them.
10.5.1 Required
This is a boolean attribute that informs the browser to submit the form only when the required fields are not left empty by the users. The input type elements, such as button, range, and color cannot be set for required attribute as they have a default value.
Different Web browsers such as Opera, Chrome, and Firefox provide different error messages, such as ‘This is a required field’, or ‘Please fill out this field’ for required attribute.
Code Snippet 13 shows assignment of required attribute to the name field on the registration form.
<label>Name: <em> <img src=”star.jpg” width=”9” height=”10”
alt=”” border=”0”> </em>
</label> <br>
<input type=”text” value=”” name=”first” size=”8” tabindex=”1”
required =”true”/>
<input type=”text” value=”” name=”last” size=”14” tabindex=”2”
required=”true”/>
<input type=”submit” value=”submit”/>
Placeholder
This attribute displays a short hint or text inside a form element. This informs the user about what data needs to be entered in that field. The placeholder text toggles, which means it appears in the field and disappears when the user clicks inside the field. Earlier, Web developers provided this functionality through JavaScript snippets which is now done in the browsers with the help of placeholder attribute. At present, all the browsers such as Chrome, Safari, Opera, and Firefox support the placeholder attribute.
If the size of the hint exceeds the field size, then use title attribute to describe text for the field.
Code Snippet 14 shows the assignment of placeholder attribute to the name field on the registration form.
<label>Name: <img src=”required_star.gif” height=”10px”
width=”10px”/></label> <br>
<input type=”text” value=”” name=”first” size=”8” tabindex=”1”
required=”true” placeholder=”First Name”/>
<input type=”text” value=”” name=”last” size=”14” tabindex=”2”
required=”true” placeholder=”Last Name” /><br/>
Pattern
This attribute uses regular expressions for validating the fields. The data entered by the user must match with the pattern specified in the regular expression. This helps to limit the input accepted from the user.
While including regular expressions through pattern attribute, it informs the users about the excepted pattern for the data. This can be achieved in the current browsers using the title attribute, which is displayed as a tool tip when the users move the pointer over the field.
You need to validate a zip code of five numbers on the form. There is no pre-defined input type to restrict the input to numbers of specified length. Thus, pattern attribute can be used to create user-defined check values for the field. Also, a title attribute can be used to customize the error message displayed for the field.
Code Snippet 15 shows the assignment of pattern attribute to the phone number field on the registration form.
<label>Phone number:<img src=”required_star.gif” height=”10px”
width=”10px”/></label>
<input type=”tel” value=”” size=”4” maxlength=”5” tabindex=”11”
required=”true” placeholder=”Code”pattern=”[+0-9]{1,4}”
title=”Format:(+)99(99)”/>
<label>-</label>
<input type=”tel” value=”” size=”10” maxlength=”12”
tabindex=”13” required=”true” placeholder=”Number” pattern=”[0-9]{8,}” title=”Minimum 8 numbers”/>
In the code, [+0-9] pattern indicates that only special character ‘+’ as well as numbers are allowed. Also, {1, 4} refers to the length of the numbers, that is between 1 and 4. Similarly, {8,} means minimum eight numbers are allowed in the tel input type field.
Multiple
This is a boolean attribute that allows multiple values for some input types. This was available only for select input type in the earlier version of HTML.
HTML5 allows multiple attribute with input types, such as email and file. If assigned, it allows selection of multiple files, or include several e-mail addresses in the email field separated by comma separator.
At present, browsers such as Chrome, Opera, and Firefox support multiple attribute for email and file element.
Code Snippet 16 shows the assignment of multiple attribute to the e-mail address field on the registration form.
Code Snippet :
<label>Email Address:<img src=”required_star.gif” height=”10px” width=”10px”/></label>
<input type=”email” value=”” name=”emailid” maxlength=”255” tabindex=”5” required=”true” placeholder=”Email Address” multiple/>
In the code, multiple attribute will allow insertion of multiple e-mail addresses in the field. Every e-mail address will be validated individually by the browser.
Autofocus
Earlier, Web developers were using JavaScript code to set the focus to the input field on page load. The purpose was to force the focus over the input field, even if the user selected some other element while page is still loading. As a result of the JavaScript code, control moves to the input field upon completion of page load. This way, regardless of what the user selected, the focus would always be on the input field.
To provide an easier solution for this behavior, HTML5 has introduced autofocus attribute for the form elements. The autofocus attribute will focus on the input field on page load. However, depending upon the situation, it will not move the focus away if the user has selected some other field. Only one element can be focused with autofocus attribute on a particular page while loading.
Code Snippet 17 shows the assignment of autofocus attribute to the first name field on the registration form.
<label>Name:</label>
<br>
<input type=”text” value=”” name=”first” size=”8” tabindex=”1”
placeholder =”First Name” autofocus/>
<input type=”submit” value=”submit”/>
<br>
<label>First Name</label>
Form
Earlier, all the form controls need to be provided between the opening and closing <form> tag. In HTML5, elements can be inserted at any place in the document and they can reference the form using the form attribute .
Code Snippet 18:
<body>
<input type=”text” name=”mytext” id=”mytext” form=”myform”/>
. . .
. . .
<form id=”myform”>
. . .
. . .
</form>
</body>
In the code, the form is declared with an id attribute. The value of the id attribute is assigned to the input element using form attribute.
Html tutorials session 10 :
Html session 10 theory :
Autocomplete Attribute :
Many browsers help user in filling forms by providing data in the input fields, such as email and tel, based on their earlier input. In many situations, the autocomplete behavior may not be secure, especially with certain fields accepting password or credit card number data.
HTML5 offers an autocomplete attribute which provides control on prefilled values displayed in the fields. It must be specified on the form element which applies for all input fields or on particular input fields. The input element that can support autocomplete are text, url, tel, password, datepickers, range, and color.
The autocomplete feature comprises two states namely, on and off. The on state indicates that the data that is not sensitive can be remembered by the browser. Similarly, the off state indicates that the data will not be remembered. Such data may be sensitive and not safe for storing with the browsers. Hence, user needs to explicitly provide the data each time while filling the form.
By default, many browsers have the autocomplete feature enabled in them. The browsers that do not support autocompletion, can be turned on or off for this behavior by specifying autocomplete attribute either on the form or specific input elements.
New Form Elements
HTML5 has introduced some brand new elements that can be incorporated in the Web pages. These new elements are specifically designed to be used with the JavaScript. When combined with JavaScript, these new elements can be more functional.
At present, all the browsers do not provide the support for these new elements. If the control is not supported by the browser, then it displays element as a text field. Opera provides the support for all the new form elements.
The new form elements introduced in HTML5 are as follows:
Datalist
Progress
Meter
Output
Datalist
Datalist is a form-specific element. It provides a text field with a set of predefined list of options that are displayed in a drop-down list. When the text field receives focus, a list of options is displayed to the user.
The <datalist> element is very similar to standard <select> element available in earlier HTML. The only difference in datalist is that it allows the user to enter data of their choice or select from the suggested list of options.
The lists of options for the <datalist> element are placed using the option element. Then, the datalist is associated with an input element using the list attribute. The value of the list attribute is the value of id attribute provided with the <datalist> element. The same datalist can be associated with several input fields. At present, only Opera browser provides the support for the datalist.
Code Snippet 20 shows the syntax of providing the <datalist> element on the form.
Code Snippet :
<label> Select the mode of payment: </label>
<input type=”text” name=”payment” list=”paymentlist” />
<datalist id=”paymentlist”>
<option value=”Cash-on-Delivery”>
<option value=”Net Banking”>
<option value=”Credit Card”>
<option value=”Debit Card”>
<option value=”e-Gift Voucher”>
</datalist>
<input type=”submit” value=”submit”/>
In the code, a datalist requires value attribute to be added with the <option> tag. Values nested between the opening and closing <option> tag will not be displayed in the datalist menu.
Progress
The progress element represents the current status of a task, which gradually changes as the task heads for completion. This is not a form-specific element.
For example, when the user downloads any file from a particular Web page, the download task is represented as a progress bar.
Code Snippet 21 shows the syntax for providing progress element on the form.
Code Snippet 21:
<label> Downloading status: </label>
<progress value=”35” max=”100” ></progress>
<input type=”submit” value=”submit”/>
In the code, the progress element contains two attributes namely, max and value. The max attribute declares the maximum value for the task to be processed for its completion.
The value attribute indicates how much task has been processed so far.
Meter
The meter element represents a measurement scale for a known range. The known range have the definite minimum and maximum values to measure the data on the scale. For example, a meter element can be used to represent measurements, such as disk usage space, fraction value, or significance of a query result. All these have a known maximum value defined for them. The meter element cannot indicate age, height, or weight, as maximum values for them cannot be specified.
Code Snippet 22 shows the code of the meter element.
Code Snippet 22:
<label> Total score of marks: </label>
0 <meter min=”0” max=”400” value=”180” title=”numbers scored” low=”120” high=”300”> </meter> 400<br/>
<input type=”submit” value=”submit”/>
In the code, the meter element contains six attributes that are used to determine the measurements in the known range.
The min and max attribute specifies the minimum and maximum value that sets bounds for the range. The default value for the max attribute is 1. The value attribute specifies the current measured value. The high and low attributes specifies the range of values that can be considered as high or low for the given range.
For example, in the given range of scores, the range of values below 120 will be considered low, but anything above 300 will be considered as high.
There is another attribute named optimum which refers to the ideal value for the measurement.
Output
The output element displays the results of a calculation on a form. The result values displayed in the output element are processed from the other form elements. For example, the output element might be used to display the total cost on the purchase items after calculating discount amount in a registration form or purchase order form.
Code Snippet 23 shows the calculation of data from other form elements to be displayed in the output element.
Code Snippet :
<form oninput=”x.value = parseInt(type.value)*
parseInt(duration.value)”>
<label>Membership Type:</label>
<select name=”type”>
<option value=”400”>Gold - $400</option>
<option value=”500”>Silver - $500</option>
<option value=”600”>Platinum - $600</option>
</select>
<label>Duration [years]:</label>
<input type=”number” value=”0” name=”duration”
min=”1”max=”5” step=”1” />
<label> Annual Payment Fees: $.</label>
<output name=”x” for=”type duration”></output>
In the code, for attribute relates the output element with the elements whose values are taken for calculation. The form oninput event handles the input event which is fired whenever the value of the elements change on receiving input from the user. A JavaScript code can also be written to update the values for the output element.
