Pre html что это

Pre html что это

В рубрике «HTML» Вы найдете бесплатные уроки по работе с этим языком гипертекстовой разметки, который лежит в основе большинства сайтов.

Данная рубрика заменит Вам полноценный «HTML учебник». Здесь Вы сможете найти ответы на большинство вопросов, связанных с HTML и DHTML.

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Лайфхак: наиполезнейшая функция var_export()

При написании или отладки PHP скриптов мы частенько пользуемся функциями var_dump() и print_r() для вывода предварительных данных массив и объектов. В этом посте я бы хотел рассказать вам о функции var_export(), которая может преобразовать массив в формат, пригодный для PHP кода.

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К примеру у вас есть поле поиска, которое обрабатывается при каждом нажатии клавиши клавиатуры. Если кто-то захочет написать слово Windows, AJAX запрос будет отправлен по следующим фрагментам: W, Wi, Win, Wind, Windo, Window, Windows. Проблема?.

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HTML-теги и атрибуты, о которых вы, возможно, не знали

Эта статья — шпаргалка по HTML-тегам. Поэтому не будем разглагольствовать, сразу к делу.

address

Тег address определяет контактную информацию об авторе или владельце документа или статьи. Контактная информацию может включать в себя адрес электронной почты, адрес сайта, физический адрес, номер телефона, ссылки на аккаунты в социальных сетях и т.д.

audio

Тег audio используется для встраивания аудио-контента (музыка и др.) в веб-страницу.

video

Тег video используется для встраивания видео-контента (видеоклип и др.) в веб-страницу.

Тег base определяет основной путь ( URL ) и/или цель ( target ) для всех относительных путей в документе. Он должен размещаться в теге head и иметь хотя бы один из следующих атрибутов:

blockquote и cite

Тег cite определяет название какой-либо работы (книги, стихотворения, песни, фильма, картины, скульптуры и т.д.). Он также может представлять из себя ссылку на источник цитаты.

Тег code используется для определения части компьютерного кода:

Для форматирования блока кода code часто используется совместно с тегом pre :

datalist

Тег datalist определяет список возможных вариантов для заполнения поля для ввода текста. Он позволяет реализовать «автозавершение» для элемента input : при установке фокуса на такое поле пользователь видит выпадающий список.

Свойство options объекта Datalist возвращает коллекцию всех элементов списка.

Внутри dd могут размещаться параграфы, изображения, ссылки, списки и т.д.

details

По умолчанию details находится в закрытом состоянии.

Внутри details могут размещаться любые теги.

Индикатором открытого состояния details является атрибут open (этот атрибут может использоваться в качестве CSS-селектора — details[open] или JavaScript-селектора — document.querySelector(‘[open]’) ).

dialog

Тег dialog определяет диалоговое окно. Он используется для создания «попапов» и модальных окон.

По умолчанию dialog находится в неактивном состоянии.

figure

Тег figure определяет обособленный (автономный) контент, такой как иллюстрации, диаграммы, фотографии, примеры кода и т.д.

Несмотря на то, что контент элемента figure формально относится к основному потоку (main flow), его позиция (местонахождение) не зависит от этого потока. Поэтому удаление элемента figure не должно влиять на поток документа.

meter

Тег meter определяет скалярное значение в пределах известного диапазона или дробного значения. Другими словами, meter определяет меру чего-либо (gauge).

Этот тег не должен использоваться в качестве индикатора прогресса.

Так можно записать уровень заряда батареи вашего устройства в значение meter :

progress

Тег progress определяет процесс выполнения задачи.

Этот тег не должен использоваться для определения меры чего-либо.

Так можно реализовать десятисекундный таймер:

output

Тег output используется для представления результата вычислений.

picture

Тег picture предоставляет возможность использования нескольких источников для изображения (нескольких изображений).

Этот тег позволяет использовать разные изображения в зависимости от ширины области просмотра (viewport width) вместо масштабирования одного изображения.

template

Тег template используется в качестве контейнера для разметки, которая не отображается при загрузке страницы.

Этот тег предназначен для хранения разметки, которая используется часто, но в определенных случаях (по запросу).

Тег time определяет конкретное время (или дату и время).

Атрибут datetime используется для представления времени в машиночитаемом формате.

noscript

Другие теги в форме шпаргалок

Семантическое «секционирование» страницы

Стилизация текста

Форма

Поля для ввода данных

Пример валидации адреса электронной почты и пароля:

Таблица

Теги colgroup и col могут использоваться для стилизации определенных колонок таблицы целиком вместо стилизации каждой ячейки и строки по отдельности.

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Pre html что это

Support in all current engines.

Support in all current engines.

While paragraphs are usually represented in visual media by blocks of text that are physically separated from adjacent blocks through blank lines, a style sheet or user agent would be equally justified in presenting paragraph breaks in a different manner, for instance using inline pilcrows (¶).

The following examples are conforming HTML fragments:

The p element should not be used when a more specific element is more appropriate.

The following example is technically correct:

However, it would be better marked-up as:

List elements (in particular, ol and ul elements) cannot be children of p elements. When a sentence contains a bulleted list, therefore, one might wonder how it should be marked up.

For instance, this fantastic sentence has bullets relating to

and is further discussed below.

The solution is to realize that a paragraph, in HTML terms, is not a logical concept, but a structural one. In the fantastic example above, there are actually five paragraphs as defined by this specification: one before the list, one for each bullet, and one after the list.

The markup for the above example could therefore be:

Authors wishing to conveniently style such «logical» paragraphs consisting of multiple «structural» paragraphs can use the div element instead of the p element.

Thus for instance the above example could become the following:

This example still has five structural paragraphs, but now the author can style just the div instead of having to consider each part of the example separately.

4.4.2 The element

Support in all current engines.

Support in all current engines.

The hr element represents a paragraph-level thematic break, e.g. a scene change in a story, or a transition to another topic within a section of a reference book.

The following fictional extract from a project manual shows two sections that use the hr element to separate topics within the section.

There is no need for an hr element between the sections themselves, since the section elements and the h1 elements imply thematic changes themselves.

The following extract from Pandora’s Star by Peter F. Hamilton shows two paragraphs that precede a scene change and the paragraph that follows it. The scene change, represented in the printed book by a gap containing a solitary centered star between the second and third paragraphs, is here represented using the hr element.

The hr element does not affect the document’s outline.

4.4.3 The element

The pre element represents a block of preformatted text, in which structure is represented by typographic conventions rather than by elements.

In the HTML syntax, a leading newline character immediately following the pre element start tag is stripped.

Some examples of cases where the pre element could be used:

Authors are encouraged to consider how preformatted text will be experienced when the formatting is lost, as will be the case for users of speech synthesizers, braille displays, and the like. For cases like ASCII art, it is likely that an alternative presentation, such as a textual description, would be more universally accessible to the readers of the document.

To represent a block of computer code, the pre element can be used with a code element; to represent a block of computer output the pre element can be used with a samp element. Similarly, the kbd element can be used within a pre element to indicate text that the user is to enter.

In the following snippet, a sample of computer code is presented.

In the following snippet, samp and kbd elements are mixed in the contents of a pre element to show a session of Zork I.

The following shows a contemporary poem that uses the pre element to preserve its unusual formatting, which forms an intrinsic part of the poem itself.

4.4.4 The element

Support in all current engines.

Support in all current engines.

The HTMLQuoteElement interface is also used by the q element.

The blockquote element represents a section that is quoted from another source.

Content inside a blockquote must be quoted from another source, whose address, if it has one, may be cited in the attribute.

If the cite attribute is present, it must be a valid URL potentially surrounded by spaces. To obtain the corresponding citation link, the value of the attribute must be parsed relative to the element’s node document. User agents may allow users to follow such citation links, but they are primarily intended for private use (e.g., by server-side scripts collecting statistics about a site’s use of quotations), not for readers.

The content of a blockquote may be abbreviated or may have context added in the conventional manner for the text’s language.

For example, in English this is traditionally done using square brackets. Consider a page with the sentence «Jane ate the cracker. She then said she liked apples and fish.»; it could be quoted as follows:

Attribution for the quotation, if any, must be placed outside the blockquote element.

For example, here the attribution is given in a paragraph after the quote:

The other examples below show other ways of showing attribution.

The IDL attribute must reflect the element’s cite content attribute.

Here a blockquote element is used in conjunction with a figure element and its figcaption to clearly relate a quote to its attribution (which is not part of the quote and therefore doesn’t belong inside the blockquote itself):

This next example shows the use of cite alongside blockquote :

This example shows how a forum post could use blockquote to show what post a user is replying to. The article element is used for each post, to mark up the threading.

This example shows the use of a blockquote for short snippets, demonstrating that one does not have to use p elements inside blockquote elements:

Examples of how to represent a conversation are shown in a later section; it is not appropriate to use the cite and blockquote elements for this purpose.

4.4.5 The element

Support in all current engines.

Support in all current engines.

The ol element represents a list of items, where the items have been intentionally ordered, such that changing the order would change the meaning of the document.

The items of the list are the li element child nodes of the ol element, in tree order.

Support in all current engines.

The attribute, if present, must be a valid integer. It is used to determine the starting value of the list.

If the ol element has a start attribute, then:

If the ol element has a reversed attribute, then return the number of owned li elements.

The attribute can be used to specify the kind of marker to use in the list, in the cases where that matters (e.g. because items are to be referenced by their number/letter). The attribute, if specified, must have a value that is identical to one of the characters given in the first cell of one of the rows of the following table. The type attribute represents the state given in the cell in the second column of the row whose first cell matches the attribute’s value; if none of the cells match, or if the attribute is omitted, then the attribute represents the decimal state.

User agents should render the items of the list in a manner consistent with the state of the type attribute of the ol element. Numbers less than or equal to zero should always use the decimal system regardless of the type attribute.

For CSS user agents, a mapping for this attribute to the ‘list-style-type’ CSS property is given in the Rendering section (the mapping is straightforward: the states above have the same names as their corresponding CSS values).

It is possible to redefine the default CSS list styles used to implement this attribute in CSS user agents; doing so will affect how list items are rendered.

The and IDL attributes must reflect the respective content attributes of the same name.

The IDL attribute must reflect the content attribute of the same name, with a default value of 1.

This means that the start IDL attribute does not necessarily match the list’s starting value, in cases where the start content attribute is omitted and the reversed content attribute is specified.

The following markup shows a list where the order matters, and where the ol element is therefore appropriate. Compare this list to the equivalent list in the ul section to see an example of the same items using the ul element.

Note how changing the order of the list changes the meaning of the document. In the following example, changing the relative order of the first two items has changed the birthplace of the author:

4.4.6 The element

Support in all current engines.

Support in all current engines.

The ul element represents a list of items, where the order of the items is not important — that is, where changing the order would not materially change the meaning of the document.

The items of the list are the li element child nodes of the ul element.

The following markup shows a list where the order does not matter, and where the ul element is therefore appropriate. Compare this list to the equivalent list in the ol section to see an example of the same items using the ol element.

Note that changing the order of the list does not change the meaning of the document. The items in the snippet above are given in alphabetical order, but in the snippet below they are given in order of the size of their current account balance in 2007, without changing the meaning of the document whatsoever:

4.4.7 The element

Support in all current engines.

Support in all current engines.

The menu element represents a toolbar consisting of its contents, in the form of an unordered list of items (represented by li elements), each of which represents a command that the user can perform or activate.

The menu element is simply a semantic alternative to ul to express an unordered list of commands (a «toolbar»).

In this example, a text-editing application uses a menu element to provide a series of editing commands:

Note that the styling to make this look like a conventional toolbar menu is up to the application.

4.4.8 The element

Support in all current engines.

Support in all current engines.

The attribute, if present, must be a valid integer. It is used to determine the ordinal value of the list item, when the li ‘s list owner is an ol element.

If the element is not being rendered, return null; the element has no list owner.

Let ancestor be the element’s parent.

Return the closest inclusive ancestor of ancestor that produces a CSS box.

Such an element will always exist, as at the very least the document element will always produce a CSS box.

If owner is an ol element, let numbering be owner ‘s starting value. Otherwise, let numbering be 1.

Loop: If i is greater than the number of list items that owner owns, then return; all of owner ‘s owned list items have been assigned ordinal values.

Let item be the i th of owner ‘s owned list items, in tree order.

If item is an li element that has a value attribute, then:

If owner is an ol element, and owner has a reversed attribute, decrement numbering by 1; otherwise, increment numbering by 1.

Go to the step labeled loop.

The IDL attribute must reflect the value of the value content attribute.

The element’s value IDL attribute does not directly correspond to its ordinal value; it simply reflects the content attribute. For example, given this list:

The ordinal values are 1, 3, and 4, whereas the value IDL attributes return 0, 3, 0 on getting.

The following example, the top ten movies are listed (in reverse order). Note the way the list is given a title by using a figure element and its figcaption element.

The markup could also be written as follows, using the reversed attribute on the ol element:

While it is conforming to include heading elements (e.g. h1 ) inside li elements, it likely does not convey the semantics that the author intended. A heading starts a new section, so a heading in a list implicitly splits the list into spanning multiple sections.

4.4.9 The element

Support in all current engines.

Support in all current engines.

The dl element represents an association list consisting of zero or more name-value groups (a description list). A name-value group consists of one or more names ( dt elements, possibly as children of a div element child) followed by one or more values ( dd elements, possibly as children of a div element child), ignoring any nodes other than dt and dd element children, and dt and dd elements that are children of div element children. Within a single dl element, there should not be more than one dt element for each name.

Name-value groups may be terms and definitions, metadata topics and values, questions and answers, or any other groups of name-value data.

The values within a group are alternatives; multiple paragraphs forming part of the same value must all be given within the same dd element.

The order of the list of groups, and of the names and values within each group, may be significant.

In order to annotate groups with microdata attributes, or other global attributes that apply to whole groups, or just for styling purposes, each group in a dl element can be wrapped in a div element. This does not change the semantics of the dl element.

The name-value groups of a dl element dl are determined using the following algorithm. A name-value group has a name (a list of dt elements, initially empty) and a value (a list of dd elements, initially empty).

Let groups be an empty list of name-value groups.

Let current be a new name-value group.

Let seenDd be false.

Let grandchild be null.

While child is not null:

If child is a div element, then:

Let grandchild be child ‘s first child.

While grandchild is not null:

Set grandchild to grandchild ‘s next sibling.

To for a node node means to follow these steps:

If node is a dt element, then:

Append node to current ‘s name.

Otherwise, if node is a dd element, then append node to current ‘s value and set seenDd to true.

When a name-value group has an empty list as name or value, it is often due to accidentally using dd elements in the place of dt elements and vice versa. Conformance checkers can spot such mistakes and might be able to advise authors how to correctly use the markup.

In the following example, one entry («Authors») is linked to two values («John» and «Luke»).

In the following example, one definition is linked to two terms.

The following example illustrates the use of the dl element to mark up metadata of sorts. At the end of the example, one group has two metadata labels («Authors» and «Editors») and two values («Robert Rothman» and «Daniel Jackson»). This example also uses the div element around the groups of dt and dd element, to aid with styling.

The following example shows the dl element used to give a set of instructions. The order of the instructions here is important (in the other examples, the order of the blocks was not important).

The following snippet shows a dl element being used as a glossary. Note the use of dfn to indicate the word being defined.

This example uses microdata attributes in a dl element, together with the div element, to annotate the ice cream desserts at a French restaurant.

Without the div element the markup would need to use the itemref attribute to link the data in the dd elements with the item, as follows.

The dl element is inappropriate for marking up dialogue. See some examples of how to mark up dialogue.

4.4.10 The element

Support in all current engines.

The dt element represents the term, or name, part of a term-description group in a description list ( dl element).

The dt element itself, when used in a dl element, does not indicate that its contents are a term being defined, but this can be indicated using the dfn element.

This example shows a list of frequently asked questions (a FAQ) marked up using the dt element for questions and the dd element for answers.

4.4.11 The element

Support in all current engines.

The dd element represents the description, definition, or value, part of a term-description group in a description list ( dl element).

4.4.12 The element

Support in all current engines.

The figure element represents some flow content, optionally with a caption, that is self-contained (like a complete sentence) and is typically referenced as a single unit from the main flow of the document.

The element can thus be used to annotate illustrations, diagrams, photos, code listings, etc.

When a figure is referred to from the main content of the document by identifying it by its caption (e.g., by figure number), it enables such content to be easily moved away from that primary content, e.g., to the side of the page, to dedicated pages, or to an appendix, without affecting the flow of the document.

If a figure element is referenced by its relative position, e.g., «in the photograph above» or «as the next figure shows», then moving the figure would disrupt the page’s meaning. Authors are encouraged to consider using labels to refer to figures, rather than using such relative references, so that the page can easily be restyled without affecting the page’s meaning.

The first figcaption element child of the element, if any, represents the caption of the figure element’s contents. If there is no child figcaption element, then there is no caption.

This example shows the figure element to mark up a code listing.

Here we see a figure element to mark up a photo that is the main content of the page (as in a gallery).

In this example, we see an image that is not a figure, as well as an image and a video that are. The first image is literally part of the example’s second sentence, so it’s not a self-contained unit, and thus figure would be inappropriate.

In this example, which could be part of a much larger work discussing a castle, nested figure elements are used to provide both a group caption and individual captions for each figure in the group:

The previous example could also be more succinctly written as follows (using title attributes in place of the nested figure / figcaption pairs):

The figure is sometimes referenced only implicitly from the content:

4.4.13 The element

Support in all current engines.

The figcaption element represents a caption or legend for the rest of the contents of the figcaption element’s parent figure element, if any.

The element can contain additional information about the source:

4.4.14 The element

Support in all current engines.

The main element represents the dominant contents of the document.

A document must not have more than one main element that does not have the hidden attribute specified.

In this example, the author has used a presentation where each component of the page is rendered in a box. To wrap the main content of the page (as opposed to the header, the footer, the navigation bar, and a sidebar), the main element is used.

In the following example, multiple main elements are used and script is used to make navigation work without a server roundtrip and to set the hidden attribute on those that are not current:

4.4.15 The element

Support in all current engines.

Support in all current engines.

Authors are strongly encouraged to view the div element as an element of last resort, for when no other element is suitable. Use of more appropriate elements instead of the div element leads to better accessibility for readers and easier maintainability for authors.

On the other hand, div elements can be useful for stylistic purposes or to wrap multiple paragraphs within a section that are all to be annotated in a similar way. In the following example, we see div elements used as a way to set the language of two paragraphs at once, instead of setting the language on the two paragraph elements separately:

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