The first article in our series provides you with your very first experience of creating a web form, including designing a simple form, implementing it using the right HTML form controls and other HTML elements, adding some very simple styling via CSS, and describing how data is sent to a server. We'll expand on each of these subtopics in more detail later on in the module.
| Prerequisites: | Basic computer literacy, and a basic understanding of HTML . |
|---|---|
| Objective: | To gain familiarity with what web forms are, what they are used for, how to think about designing them, and the basic HTML elements you'll need for simple cases. |
Web forms are one of the main points of interaction between a user and a web site or application. Forms allow users to enter data, which is generally sent to a web server for processing and storage (see Sending form data later in the module), or used on the client-side to immediately update the interface in some way (for example, add another item to a list, or show or hide a UI feature).
A web form's HTML is made up of one or more
form controls
(sometimes called
widgets
), plus some additional elements to help structure the overall form — they are often referred to as
HTML 表单
.
The controls can be single or multi-line text fields, dropdown boxes, buttons, checkboxes, or radio buttons, and are mostly created using the
<input>
element, although there are some other elements to learn about too.
Form controls can also be programmed to enforce specific formats or values to be entered ( form validation ), and paired with text labels that describe their purpose to both sighted and blind users.
Before starting to code, it's always better to step back and take the time to think about your form. Designing a quick mockup will help you to define the right set of data you want to ask your user to enter. From a user experience (UX) point of view, it's important to remember that the bigger your form, the more you risk frustrating people and losing users. Keep it simple and stay focused: ask only for the data you absolutely need.
Designing forms is an important step when you are building a site or application. It's beyond the scope of this article to cover the user experience of forms, but if you want to dig into that topic you should read the following articles:
In this article, we'll build a simple contact form. Let's make a rough sketch.
Our form will contain three text fields and one button. We are asking the user for their name, their e-mail and the message they want to send. Hitting the button will send their data to a web server.
Ok, let's have a go at creating the HTML for our form. We will use the following HTML elements:
<form>
,
<label>
,
<input>
,
<textarea>
，和
<button>
.
Before you go any further, make a local copy of our simple HTML template — you'll enter your form HTML into here.
<form>
element
All forms start with a
<form>
element, like this:
<form action="/my-handling-form-page" method="post">
</form>
This element formally defines a form. It's a container element like a
<section>
or
<footer>
element, but specifically for containing forms; it also supports some specific attributes to configure the way the form behaves. All of its attributes are optional, but it's standard practice to always set at least the
action
and
方法
attributes:
action
attribute defines the location (URL) where the form's collected data should be sent when it is submitted.
方法
attribute defines which HTTP method to send the data with (usually
get
or
post
).
注意： We'll look at how those attributes work in our Sending form data article later on.
For now, add the above
<form>
element into your HTML
<body>
.
<label>
,
<input>
，和
<textarea>
元素
Our contact form is not complex: the data entry portion contains three text fields, each with a corresponding
<label>
:
<textarea>
; a multiline text field.
In terms of HTML code we need something like the following to implement these form widgets:
<form action="/my-handling-form-page" method="post">
<ul>
<li>
<label for="name">Name:</label>
<input type="text" id="name" name="user_name">
</li>
<li>
<label for="mail">E-mail:</label>
<input type="email" id="mail" name="user_email">
</li>
<li>
<label for="msg">Message:</label>
<textarea id="msg" name="user_message"></textarea>
</li>
</ul>
</form>
Update your form code to look like the above.
<li>
elements are there to conveniently structure our code and make styling easier (see later in the article).
For usability and accessibility, we include an explicit label for each form control.
Note the use of the
for
attribute on all
<label>
elements, which takes as its value the
id
of the form control with which it is associated — this is how you associate a form control with its label.
There is great benefit to doing this — it associates the label with the form control, enabling mouse, trackpad, and touch device users to click on the label to activate the corresponding control, and it also provides an accessible name for screen readers to read out to their users. You'll find further details of form labels in How to structure a web form .
在
<input>
element, the most important attribute is the
type
属性。
This attribute is extremely important because it defines the way the
<input>
element appears and behaves.
You'll find more about this in the
Basic native form controls
article later on.
Last but not least, note the syntax of
<input>
vs.
<textarea></textarea>
.
This is one of the oddities of HTML.
<input>
tag is an empty element, meaning that it doesn't need a closing tag.
<textarea>
is not an empty element, meaning it should be closed with the proper ending tag.
This has an impact on a specific feature of forms: the way you define the default value.
To define the default value of an
<input>
element you have to use the
value
attribute like this:
<input type="text" value="by default this element is filled with this text">
On the other hand, if you want to define a default value for a
<textarea>
, you put it between the opening and closing tags of the
<textarea>
element, like this:
<textarea>
by default this element is filled with this text
</textarea>
<button>
element
The markup for our form is almost complete; we just need to add a button to allow the user to send, or "submit", their data once they have filled out the form.
This is done by using the
<button>
element; add the following just above the closing
</ul>
tag:
<li class="button">
<button type="submit">Send your message</button>
</li>
<button>
element also accepts a
type
attribute — this accepts one of three values:
submit
,
reset
，或
button
.
submit
button (the default value) sends the form's data to the web page defined by the
action
属性在
<form>
元素。
reset
button resets all the form widgets to their default value immediately. From a UX point of view, this is considered bad practice, so you should avoid using this type of button unless you really have a good reason to include one.
button
button does... nothing! That sounds silly, but it's amazingly useful for building custom buttons — you can define their chosen functionality with JavaScript.
注意：
还可以使用
<input>
element with the corresponding
type
to produce a button, for example
<input type="submit">
. The main advantage of the
<button>
element is that the
<input>
element only allows plain text in its label whereas the
<button>
element allows full HTML content, allowing more complex, creative button content.
Now that you have finished writing your form's HTML code, try saving it and looking at it in a browser. At the moment, you'll see that it looks rather ugly.
注意： If you don't think you've got the HTML code right, try comparing it with our finished example — see first-form.html ( also see it live ).
Forms are notoriously tricky to style nicely. It is beyond the scope of this article to teach you form styling in detail, so for the moment we will just get you to add some CSS to make it look OK.
First of all, add a
<style>
element to your page, inside your HTML head. It should look like so:
<style>
</style>
Inside the
style
tags, add the following CSS:
form {
/* Center the form on the page */
margin: 0 auto;
width: 500px;
/* Form outline */
padding: 1em;
border: 1px solid #CCC;
border-radius: 1em;
}
ul {
list-style: none;
padding: 0;
margin: 0;
}
form li + li {
margin-top: 1em;
}
label {
/* Uniform size & alignment */
display: inline-block;
width: 90px;
text-align: right;
}
input,
textarea {
/* To make sure that all text fields have the same font settings
By default, textareas have a monospace font */
font: 1em sans-serif;
/* Uniform text field size */
width: 300px;
box-sizing: border-box;
/* Match form field borders */
border: 1px solid #999;
}
input:focus,
textarea:focus {
/* Additional highlight for focused elements */
border-color: #000;
}
textarea {
/* Align multiline text fields with their labels */
vertical-align: top;
/* Provide space to type some text */
height: 5em;
}
.button {
/* Align buttons with the text fields */
padding-left: 90px; /* same size as the label elements */
}
button {
/* This extra margin represent roughly the same space as the space
between the labels and their text fields */
margin-left: .5em;
}
Save and reload, and you'll see that your form should look much less ugly.
注意： You can find our version on GitHub at first-form-styled.html ( also see it live ).
The last part, and perhaps the trickiest, is to handle form data on the server side.
<form>
element defines where and how to send the data thanks to the
action
and
方法
属性。
We provide a
名称
to each form control.
The names are important on both the client- and server-side; they tell the browser which name to give each piece of data and, on the server side, they let the server handle each piece of data by name.
The form data is sent to the server as name/value pairs.
To name the data in a form you need to use the
名称
attribute on each form widget that will collect a specific piece of data.
Let's look at some of our form code again:
<form action="/my-handling-form-page" method="post">
<ul>
<li>
<label for="name">Name:</label>
<input type="text" id="name" name="user_name" />
</li>
<li>
<label for="mail">E-mail:</label>
<input type="email" id="mail" name="user_email" />
</li>
<li>
<label for="msg">Message:</label>
<textarea id="msg" name="user_message"></textarea>
</li>
...
In our example, the form will send 3 pieces of data named "
user_name
", "
user_email
", and "
user_message
".
That data will be sent to the URL "
/my-handling-form-page
" using the
HTTP
POST
方法。
On the server side, the script at the URL "
/my-handling-form-page
" will receive the data as a list of 3 key/value items contained in the HTTP request.
The way this script will handle that data is up to you.
Each server-side language (PHP, Python, Ruby, Java, C#, etc.) has its own mechanism of handling form data.
It's beyond the scope of this guide to go deeply into that subject, but if you want to know more, we have provided some examples in our
Sending form data
article later on.
Congratulations, you've built your first web form. It looks like this live:
That's only the beginning, however — now it's time to take a deeper look. Forms have way more power than what we saw here and the other articles in this module will help you to master the rest.
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