Re: Type 2 Phone
Sondra Pevy
elements of type tel are used to let the user enter and edit a telephone number. Unlike and , the input value is not automatically validated to a particular format before the form can be submitted, because formats for telephone numbers vary so much around the world.
The values of the list attribute is the id of a element located in the same document. The provides a list of predefined values to suggest to the user for this input. Any values in the list that are not compatible with the type are not included in the suggested options. The values provided are suggestions, not requirements: users can select from this predefined list or provide a different value.
The maximum string length (measured in UTF-16 code units) that the user can enter into the telephone number field. This must be an integer value of 0 or higher. If no maxlength is specified, or an invalid value is specified, the telephone number field has no maximum length. This value must also be greater than or equal to the value of minlength.
The minimum string length (measured in UTF-16 code units) that the user can enter into the telephone number field. This must be a non-negative integer value smaller than or equal to the value specified by maxlength. If no minlength is specified, or an invalid value is specified, the telephone number input has no minimum length.
The pattern attribute, when specified, is a regular expression that the input's value must match for the value to pass constraint validation. It must be a valid JavaScript regular expression, as used by the RegExp type, and as documented in our guide on regular expressions; the 'u' flag is specified when compiling the regular expression so that the pattern is treated as a sequence of Unicode code points, instead of as ASCII. No forward slashes should be specified around the pattern text.
Note: Use the title attribute to specify text that most browsers will display as a tooltip to explain what the requirements are to match the pattern. You should also include other explanatory text nearby.
The placeholder attribute is a string that provides a brief hint to the user as to what kind of information is expected in the field. It should be a word or short phrase that demonstrates the expected type of data, rather than an explanatory message. The text must not include carriage returns or line feeds.
If the control's content has one directionality (LTR or RTL) but needs to present the placeholder in the opposite directionality, you can use Unicode bidirectional algorithm formatting characters to override directionality within the placeholder; see How to use Unicode controls for bidi text for more information.
Note: Avoid using the placeholder attribute if you can. It is not as semantically useful as other ways to explain your form, and can cause unexpected technical issues with your content. See labels for more information.
The size attribute is a numeric value indicating how many characters wide the input field should be. The value must be a number greater than zero, and the default value is 20. Since character widths vary, this may or may not be exact and should not be relied upon to be so; the resulting input may be narrower or wider than the specified number of characters, depending on the characters and the font (font settings in use).
This does not set a limit on how many characters the user can enter into the field. It only specifies approximately how many can be seen at a time. To set an upper limit on the length of the input data, use the maxlength attribute.
Telephone numbers are a very commonly collected type of data on the web. When creating any kind of registration or e-commerce site, for example, you will likely need to ask the user for a telephone number, whether for business purposes or for emergency contact purposes. Given how commonly-entered phone numbers are, it's unfortunate that a "one size fits all" solution for validating phone numbers is not practical.
Sometimes it's helpful to offer an in-context hint as to what form the input data should take. This can be especially important if the page design doesn't offer descriptive labels for each . This is where placeholders come in. A placeholder is a value that demonstrates the form the value should take by presenting an example of a valid value, which is displayed inside the edit box when the element's value is "". Once data is entered into the box, the placeholder disappears; if the box is emptied, the placeholder reappears.
The physical size of the input box can be controlled using the size attribute. With it, you can specify the number of characters the input box can display at a time. In this example, for instance, the tel edit box is 20 characters wide:
The size is separate from the length limitation on the entered telephone number. You can specify a minimum length, in characters, for the entered telephone number using the minlength attribute; similarly, use maxlength to set the maximum length of the entered telephone number.
Taking it a step further, you can provide a list of default phone number values from which the user can select. To do this, use the list attribute. This doesn't limit the user to those options, but does allow them to select commonly-used telephone numbers more quickly. This also offers hints to autocomplete. The list attribute specifies the ID of a element, which in turn contains one element per suggested value; each option's value is the corresponding suggested value for the telephone number entry box.
With the element and its s in place, the browser will offer the specified values as potential values for the phone number; this is typically presented as a popup or drop-down menu containing the suggestions. While the specific user experience may vary from one browser to another, typically clicking in the edit box presents a drop-down of the suggested phone numbers. Then, as the user types, the list is adjusted to show only filtered matching values. Each typed character narrows down the list until the user makes a selection or types a custom value.
Warning: HTML form validation is not a substitute for server-side scripts that ensure the entered data is in the proper format before it is allowed into the database. It's far too easy for someone to make adjustments to the HTML that allow them to bypass the validation, or to remove it entirely. It's also possible for someone to bypass your HTML entirely and submit the data directly to your server. If your server-side code fails to validate the data it receives, disaster could strike when improperly-formatted data (or data which is too large, is of the wrong type, and so forth) is entered into your database.
If you want to further restrict entered numbers so they also have to conform to a specific pattern, you can use the pattern attribute, which takes as its value a regular expression that entered values have to match.
In this example, we present a simple interface with a element that lets the user choose which country they're in, and a set of elements to let them enter each part of their phone number; there is no reason why you can't have multiple tel inputs.
Each input has a placeholder attribute to show a hint to sighted users about what to enter into it, a pattern to enforce a specific number of characters for the desired section, and an aria-label attribute to contain a hint to be read out to screen reader users about what to enter into it.
This is an interesting idea, which goes to show a potential solution to the problem of dealing with international phone numbers. You would have to extend the example of course to provide the correct pattern for potentially every country, which would be a lot of work, and there would still be no foolproof guarantee that the users would enter their numbers correctly.
It makes you wonder if it is worth going to all this trouble on the client-side, when you could just let the user enter their number in whatever format they wanted on the client-side and then validate and sanitize it on the server. But this choice is yours to make.
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