# Table: Column Toggle

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## Column toggle table mode

- Basics
- Options
- Methods
- Events

This table mode automatically hides less important columns at narrower widths and surfaces a button to open a menu that allows the user to choose what columns they want to see. In this mode, the author attempts to define which columns are most important to show across various widths by assigning a priority to each column.

A user may choose to check as many columns as they want by tapping the "Columns..." button to open the column chooser popup. The popup contains a dynamically generated list of columns based on the table markup that can be checked and unchecked to adjust the visible columns.

Rank | Movie Title | Year | Rating | Reviews
--- | --- | --- | --- | ---
1 | Citizen Kane | 1941 | 100% | 74
2 | Casablanca | 1942 | 97% | 64
3 | The Godfather | 1972 | 97% | 87
4 | Gone with the Wind | 1939 | 96% | 87
5 | Lawrence of Arabia | 1962 | 94% | 87
6 | Dr. Strangelove Or How I Learned to Stop Worrying and Love the Bomb | 1964 | 92% | 74
7 | The Graduate | 1967 | 91% | 122
8 | The Wizard of Oz | 1939 | 90% | 72
9 | Singin' in the Rain | 1952 | 89% | 85
10 | Inception | 2010 | 84% | 78

### Applying column chooser mode to a table

The column chooser mode requires a `table` element with two attributes: `data-role="table"` and `data-mode="columntoggle"`. An `ID` attribute is also required on the table to associate it with the column chooser popup menu.

    <table data-role="table" data-mode="columntoggle" id="my-table">

### How column toggle mode works

The plugin automates a few key things: it injects the column chooser button, and generates the popup with check list of columns that can be hidden or shown by the user. The list of columns in the chooser menu is populated by parsing the values (or `abbr title`) of the first row of header (`TH`) elements. Only headers that have a `data-priority` attribute are included in the column chooser; headers without this attribute won't made available in the chooser to allow developers to identify critical columns that shouldn't be hidden. If columns are hidden via responsive media queries, these will be unchecked in the chooser to reflect the current column visibility.

The automatic column hiding behavior is accomplished by CSS media queries that hide or show columns based on priority levels at various screen widths. Since each site will have different content and column configurations, we provide a simple media query block that you can copy, paste and customize for each project. This is explained in detail below.

The priorities assigned to headers and media queries used to hide columns act as a sensible default for showing the most important columns that will fit on a device. The column chooser menu gives users the ability to override these defaults and choose which columns they want to see. These user preferences take precedence over the priority mappings so if a column is manually checked, it will remain visible across all screen widths until the page is refreshed.

Because of the flexibility this plugin provides, it's possible for users to introduce horizontal scrolling if the data in each column is long or if many columns are selected to be shown on a smaller screen.

### Setting column priority

The table works by hiding and showing columns based on two inputs: available screen width or by the user checking and unchecking which columns to display in a column picker popup. Add `data-priority` attributes to each of the table headers of columns you want to responsively display and assign a priority (1 = highest, 6 = lowest). Any table header given a priority will be available in the column picker menu.

To make a column persistent so it's not available for hiding, omit the `data-priority` attribute. This will make the column visible at all widths and won't be available in the column chooser menu.

    <th>I'm am critical and can't be removed</th>
    <th data-priority="1">I'm very important</th>
    <th data-priority="3">I'm somewhat</th>
    <th data-priority="5">I'm less important</th>

Behind the scenes, the plugin will apply classes to each cell that map to the priority set in the data attribute on the header. For example, if a table heading has a `data-priority="3"` attribute, every cell in that column will assigned a `ui-table-priority-3` class once enhanced. These classes are then used in media queries to hide and show columns based on screen width (see below).

    <td class="ui-table-priority-3">97%</td>

You may use any priority naming convention and assign as many (or few) levels of priority for the columns. The plugin simply generates class names based on the values in the `data-priority` attribute so even though we default to using a numeric system of 1-6, any naming convention is possible.

For example, if a priority of `data-priority="critical"` is added to the heading, a class of `ui-table-priority-critial` will be applied to each cell in that column. If a priority is assigned, the column will be made available for the toggling in the column menu and adds the classes to each cell, the rest of the styling and media query creation is up to you write in your custom stylesheet.

### Making the table responsive

The styles for the all priority columns (1-6) start as `display:none` in the structure stylesheet since we're taking a mobile-first approach to our styles. This means that only columns that should be persistent are visible in the styles to start.

The framework does not automatically include the the media queries to progressively display columns at wider widths. We do this to make it easier for developers to customize the media query widths for each priority level.

Media queries add the responsive behavior to show and hide columns by priority. Each media query is written using `min-width` widths so they build on top of each other. The widths are set in ems so they respond to font size changes. To calculate a pixel withs in em's, divide the target width by 16 (pixels) - it's that easy.

Inside each media query, we override the `display:none` style properties set on all the priority columns in the basic styles to `display:table-cell` so they become visible again and act as a table.

To customize the breakpoints, copy the following style block into your custom style overrides and adjust the `min-width` media query values for each priority level to specify where various priority columns should appear.

In the example styles below for a `my-custom-class` class on the table, the priority 1 columns are shown first, at widths above `20em` (320px), then priority 2 kicks in above `30em` (480px) and so on up to wide desktop widths with priority 6. Feel free to change these breakpoints in your stylesheet and choose how many priority levels you'd like to use.

    /* Show priority 1 at 320px (20em x 16px) */
    @media screen and (min-width: 20em) {
       .my-custom-class th.ui-table-priority-1,
       .my-custom-class td.ui-table-priority-1 {
         display: table-cell;
       }
    }
    /* Show priority 2 at 480px (30em x 16px) */
    @media screen and (min-width: 30em) {
       .my-custom-class  th.ui-table-priority-2,
       .my-custom-class td.ui-table-priority-2 {
         display: table-cell;
       }
    }
    ...more breakpoints...

Due to CSS specificity, you will also need to include the class definitions for the hidden and visible states after the custom breakpoints in your custom stylesheet so be sure to include these as well:

    /* Manually hidden */
    .my-custom-class th.ui-table-cell-hidden,
    .my-custom-class td.ui-table-cell-hidden {
      display: none;
    }

    /* Manually shown */
    .my-custom-class th.ui-table-cell-visible,
    .my-custom-class td.ui-table-cell-visible {
       display: table-cell;
    }

### Applying a preset breakpoint

Even though we strongly encourage you to write custom breakpoints yourself, the framework includes a set of pre-configured breakpoints for each of the six priority levels that you can use if they happen work well for your content.

These breakpoints can applied by adding a `class="ui-responsive"` to the table element. Here is an example of a table with this class added:

    <table data-role="table" class="ui-responsive" data-mode="columntoggle" id="my-table">

The six preset breakpoints classes included in the column toggle stylesheet use regular increments of 10em (160 pixels). Here is a summary of the breakpoints assigned to each priority in the preset styles:

`data-priority="1"`
  Displays the column at 320px (20em)
`data-priority="2"`
  Displays the column at 480px (30em)
`data-priority="3"`
  Displays the column at 640px (40em)
`data-priority="4"`
  Displays the column at 800px (50em)
`data-priority="5"`
  Displays the column at 960px (60em)
`data-priority="6"`
  Displays the column at 1,120px (70em)

If these preset breakpoints don't work for your content and layout needs, we recommend that you create custom breakpoints to fine tune the styles.

### Working with the column menu classes

When the column chooser menu opens, the column checkboxes will be checked or unchecked based on the visibility of each column based on the media queries so it accurately reflects what is being seen. These media queries to hide or show columns act as sensible defaults for what columns should be shown based on the developer's understanding of the column importance and data values. The chooser menu allows the user to have control of the table presentation so this takes precedence over the default display.

If an unchecked column checkbox is checked by the user, they now take control of the column. Until the page is refreshed, the visibility of that column will now always be visible, even if the screen is re-sized. Behind the scenes, a class of `ui-table-cell-visible` is added to all the cells in that column to ensure they override any visibility set via media queries.

The same idea applies when a column is unchecked: from then on, the column won't be seen at any width because the class of `ui-table-cell-hidden` is added to each of the cells in that column.

### Styling the button and column chooser popup

The column chooser popup is opened via a button that is generated by the framework. The button's text is "Columns..." by default but can be set by adding the `data-column-btn-text` attribute to the table to the text string you want in the button. The button will inherit the theme from the content area, just like all buttons, but the theme can be set manually by adding the `data-column-btn-theme` attribute to any swatch letter in your theme.

This button is injected directly before the table element and has basic styles to align it to the right but you may want to further customize the appearance of this button. To style all these buttons across your site, key off the `ui-table-columntoggle-btn` structural class on this link.

To target styles against only a specific button, use the unique `href` value that is generated to target a specific column chooser button. For example, a table with an `ID` of `movie-table` will generate a popup with an `ID` of `movie-table-popup` so a CSS selector of `a[href="#movie-table-popup"]` will target only the column popup button for this specific table.

The theme for the column chooser popup can be set by adding the `data-column-popup-theme` attribute to the table and specifying any swatch letter in your theme. For custom styles or scripting, all the column chooser popups can be targeted by using the `ui-table-columntoggle-popup` structural class added to these popups. To customize a single popup, use the generated `ID` based on the table `ID` that added to each specific popup (such as `#movie-table-popup`) to target a specific popup.

### Working with grouped column headers

It's fairly common to need to logically group multiple columns together under a heading group for financial or scientific data. The framework can support the most simple version of this by allowing for two rows of table headers (`TH`), with the first row containing simple `colspan` attributes to group the columns below. In this configuration, the framework will parse the first row only for the priority and expose these heading groups as the options in the column chooser popup. In this configuration, the second heading will not be exposed as columns that can be hidden or shown independently of the groupings in the chooser.

### In this section

- Tables
- Reflow mode
- Column toggle mode