No segundo artigo neste módulo, nós vamos ver algumas funcionalidades mais avançadas das tabelas HTML tables — tais como legendas/resumos e agrupar as suas filas no cabçalho da taela, secções de corpo e rodapé — bem como, ver a acessibilidade das tabelas para os utilizadores deficientes visuais.

Adicionar uma legenda à sua tabela com <caption>

Pré-requisitos:	The basics of HTML (see Introduction to HTML).
Objetivo:	To learn about more advanced HTML table features, and the accessibility of tables.

You can give your table a caption by putting it inside a {{htmlelement("caption")}} element and nesting that inside the {{htmlelement("table")}} element. You should put it just below the opening <table> tag.

As you can infer from the brief example above, the caption is meant to contain a description of the table contents. This is useful for all readers wishing to get a quick idea of whether the table is useful to them as they scan the page, but particularly for blind users. Rather than have a screenreader read out the contents of many cells just to find out what the table is about, he or she can rely on a caption and then decide whether or not to read the table in greater detail.

Nota: The {{htmlattrxref("summary","table")}} attribute can also be used on the <table> element to provide a description — this is also read out by screenreaders. We'd recommend using the <caption> element instead, however, as summary is {{glossary("deprecated")}} by the HTML5 spec, and can't be read by sighted users (it doesn't appear on the page.)

Aprendizagem ativa: Adicionar uma caption

Adding structure with <thead>, <tfoot>, and <tbody>

As your tables get a bit more complex in structure, it is useful to give them more structural definition. One clear way to do this is by using {{htmlelement("thead")}}, {{htmlelement("tfoot")}}, and {{htmlelement("tbody")}}, which allow you to mark up a header, footer, and body section for the table.

These elements don't make the table any more accessible to screenreader users, and don't result in any visual enhancement on their own. They are however very useful for styling and layout — acting as useful hooks for adding CSS to your table. To give you some interesting examples, in the case of a long table you could make the table header and footer repeat on every printed page, and you could make the table body display on a single page and have the contents available by scrolling up and down.

Note: <tbody> is always included in every table, implicitly if you don't specify it in your code. To check this, open up one of your previous examples that doesn't include <tbody> and look at the HTML code in your browser developer tools — you will see that the browser has added this tag for you. You might wonder why you ought to bother including it at all — you should, because it gives you more control over your table structure and styling.

Aprendizagem ativa: Adicionar uma estrutura de tabela

Nota: We don't expect you to fully understand the CSS right now. You'll learn more about this when you go through our CSS modules (Introduction to CSS is a good place to start; we also have an article specifically on styling tables).

Hidden example

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>My spending record</title>
    <style>

        html {
          font-family: sans-serif;
        }

          table {
          border-collapse: collapse;
          border: 2px solid rgb(200,200,200);
          letter-spacing: 1px;
          font-size: 0.8rem;
        }

        td, th {
          border: 1px solid rgb(190,190,190);
          padding: 10px 20px;
        }

        th {
          background-color: rgb(235,235,235);
        }

        td {
          text-align: center;
        }

        tr:nth-child(even) td {
          background-color: rgb(250,250,250);
        }

        tr:nth-child(odd) td {
          background-color: rgb(245,245,245);
        }

        caption {
          padding: 10px;
        }

        tbody {
          font-size: 90%;
          font-style: italic;
        }

        tfoot {
          font-weight: bold;
        }
    </style>
  </head>
  <body>
      <table>
        <caption>How I chose to spend my money</caption>
        <thead>
          <tr>
            <th>Purchase</th>
            <th>Location</th>
            <th>Date</th>
            <th>Evaluation</th>
            <th>Cost (€)</th>
          </tr>
        </thead>
        <tfoot>
          <tr>
            <td colspan="4">SUM</td>
            <td>118</td>
          </tr>
        </tfoot>
        <tbody>
          <tr>
            <td>Haircut</td>
            <td>Hairdresser</td>
            <td>12/09</td>
            <td>Great idea</td>
            <td>30</td>
          </tr>
          <tr>
            <td>Lasagna</td>
            <td>Restaurant</td>
            <td>12/09</td>
            <td>Regrets</td>
            <td>18</td>
          </tr>
          <tr>
            <td>Shoes</td>
            <td>Shoeshop</td>
            <td>13/09</td>
            <td>Big regrets</td>
            <td>65</td>
          </tr>
          <tr>
            <td>Toothpaste</td>
            <td>Supermarket</td>
            <td>13/09</td>
            <td>Good</td>
            <td>5</td>
          </tr>
        </tbody>
    </table>

  </body>
</html>

Incorporar Tabelas

It is possible to nest a table inside another one, as long as you include the complete structure, including the <table> element. This is generally not really advised, as it makes the markup more confusing and less accessible to screenreader users, and in many cases you might as well just insert extra cells/rows/columns into the existing table. It is however sometimes necessary, for example if you want to import content easily from other sources.

Tabelas para utilizadores deficientes visuais

Let's recap briefly on how we use data tables. A table can be a handy tool, for giving us quick access to data and allowing us to look up different values. For example, It takes only a short glance at the table below to find out how many rings were sold in Gent last August. To understand its information we make visual associations between the data in this table and its column and/or row headers.

But what if you cannot make those visual associations? How then can you read a table like the above? Visually impaired people often use a screenreader that reads out information on web pages to them. This is no problem when you're reading plain text but interpreting a table can be quite a challenge for a blind person. Nevertheless, with the proper markup we can replace visual associations by programmatic ones.

This section of the article provides further techniques for making tables as accessible as possible.

Utilizar os cabeçalhos de coluna e linha

Screenreaders will identify all headers and use them to make programmatic associations between those headers and the cells they relate to. The combination of column and row headers will identify and interpret the data in each cell so that screenreader user can interpret the table similarly to how a sighted user does.

Items Sold August 2016
		Clothes	Accessories
		Trousers	Skirts	Dresses	Bracelets	Rings
Belgium	Antwerp	56	22	43	72	23
Gent	46	18	50	61	15
Brussels	51	27	38	69	28
The Netherlands	Amsterdam	89	34	69	85	38
Utrecht	80	12	43	36	19

O atributo de scope

A new topic for this article is the {{htmlattrxref("scope","th")}} attribute, which can be added to the <th> element to tell screenreaders exactly what cells the header is a header for — is it a header for the row it is in, or the column, for example? Looking back to our spending record example from earlier on, you could unambiguously define the column headers as column headers like this:

And each row could have a header defined like this (if we added row headers as well as column headers):

Screenreaders will recognize markup structured like this, and allow their users to read out the entire column or row at once, for example.

scope has two more possible values — colgroup and rowgroup. these are used for headings that sit over the top of multiple columns or rows. If you look back at the "Items sold..." table at the start of this section of the article, you'll see that the "Clothes" cell sits above the "Trousers", "Skirts", and "Dresses" cells. All of these cells should be marked up as headers (<th>), but "Clothes" is a heading that sits over the top and defines the other three subheadings. "Clothes" therefore should get an attribute of scope="colgroup", whereas the others would get an attribute of scope="col".

A identificação e atributos de cabeçalhos

An alternative to using the scope attribute is to use {{htmlattrxref("id")}} and {{htmlattrxref("headers", "td")}} attributes to create associations between headers and cells. The way they are used is as follows:

This gives your HTML table an explicit definition of the position of each cell in the table, defined by the header(s) for each column and row it is part of, kind of like a spreadsheet. For it to work well, the table really needs both column and row headers.

Returning to our spending costs example, the previous two snippets could be rewritten like this:

Nota: This method creates very precise associations between headers and data cells but it uses a lot more markup and does not leave any room for errors. The scope approach is usually enough for most tables.

Aprendizagem ativa: manipular scope e cabeçalhos

Resumo

There are a few other things you could learn about table HTML, but we have really given all you need to know at this moment in time. At this point, you might want to go and learn about styling HTML tables — see Styling Tables.