Observable Framework Input Checkbox

The initial value of a checkbox defaults to an empty array. You can override this by specifying the value option, which should also be an array (or iterable).

const colors = view(Inputs.checkbox(["red", "green", "blue"], {label: "color"}));

colors

A checkbox’s values need not be strings: they can be anything. Specify a format function to control how these values are presented to the reader.

const teams = [
  {name: "Lakers", location: "Los Angeles, California"},
  {name: "Warriors", location: "San Francisco, California"},
  {name: "Celtics", location: "Boston, Massachusetts"},
  {name: "Nets", location: "New York City, New York"},
  {name: "Raptors", location: "Toronto, Ontario"},
];

const watching = view(Inputs.checkbox(teams, {label: "Watching", format: (x) => x.name}));

watching

A checkbox can be disabled by setting the disabled option to true. Alternatively, specific options can be disabled by passing an array of values to disable.

const vowels = view(Inputs.checkbox([..."AEIOUY"], {label: "Vowel", disabled: ["Y"]}));

vowels

The format function, like the label, can return either a text string or an HTML element. This allows extensive control over the appearance of the checkbox, if desired.

const colors2 = view(
  Inputs.checkbox(["red", "green", "blue"], {
    value: ["red"],
    label: html`<b>Colors</b>`,
    format: (x) =>
      html`<span style="
          text-transform: capitalize;
          border-bottom: solid 2px ${x};
          margin-bottom: -2px;
        ">${x}</span>`
  })
);

colors2

If the checkbox’s data are specified as a Map, the values will be the map’s values while the keys will be the displayed options. (This behavior can be customized by passing keyof and valueof function options.) Below, the displayed sizes are named, but the value is the corresponding number of fluid ounces.

const sizes = view(
  Inputs.checkbox(
    new Map([
      ["Short", 8],
      ["Tall", 12],
      ["Grande", 16],
      ["Venti", 20]
    ]),
    {value: [12], label: "Size"}
  )
);

sizes

Since the format function is passed elements from the data, it can access both the key and value from the corresponding Map entry.

const size2 = view(
  Inputs.checkbox(
    new Map([
      ["Short", 8],
      ["Tall", 12],
      ["Grande", 16],
      ["Venti", 20]
    ]),
    {value: [12], label: "Size", format: ([name, value]) => `${name} (${value} oz)`}
  )
);

size2

Passing a Map to checkbox is especially useful in conjunction with d3.group. For example, given a the sample olympians dataset of Olympic athletes, we can use d3.group to group them by gold medal count, and then checkbox to select the athletes for the chosen count. Note that the value of the checkbox will be an array of arrays, since d3.group returns a Map from key to array; use array.flat to merge these arrays if desired.

const goldAthletes = view(
  Inputs.checkbox(
    d3.group(olympians, (d) => d.gold),
    {label: "Gold medal count", sort: "descending", key: [4, 5]}
  )
);

goldAthletes.flat()

If the sort and unique options are specified, the checkbox’s keys will be sorted and duplicate keys will be discarded, respectively.

const bases = view(Inputs.checkbox("GATTACA", {sort: true, unique: true}));

bases

Options

Inputs.checkbox(data, options)

The available checkbox input options are:

• label - a label; either a string or an HTML element
• sort - true, ascending, descending, or a comparator to sort keys; defaults to false
• unique - true to only show unique keys; defaults to false
• locale - the current locale; defaults to English
• format - a format function; defaults to formatLocaleAuto composed with keyof
• keyof - a function to return the key for the given element in data
• valueof - a function to return the value of the given element in data
• value - the initial value, an array; defaults to an empty array (no selection)
• disabled - whether input is disabled, or the disabled values; defaults to false