Form Spinbutton

Spin buttons are a BootstrapVue custom numerical range form control. Spin buttons allow for incrementing or decrementing a numerical value within a range of a minimum and maximum number, with optional step value.

Overview

The component <b-form-spinbutton> is WAI-ARIA compliant, allowing for keyboard control, and supports both horizontal (default) and vertical layout.

Similar to range type inputs, BootstrapVue's <b-form-spinbutton> does not allow the user to type in a value.

<template>
  <div>
    <label for="demo-sb">Spin Button</label>
    <b-form-spinbutton id="demo-sb" v-model="value" min="1" max="100"></b-form-spinbutton>
    <p>Value: {{ value }}</p>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        value: 50
      }
    }
  }
</script>

<!-- b-form-spinbutton-demo.vue -->

The ArrowUp and ArrowDown keys can be used to increment or decrement the value.

To be submitted via native browser form submits, the spinbutton must have a name set via the name prop. This will create a hidden input containing the current value of the spinbutton. If the spinbutton does not have a value, the hidden input's value will be an empty string.

v-model value

The v-model always returns the value as a number. The v-model can be null if no initial value is set.

If the initial value is null no value will be displayed in the spinbutton. Use the placeholder prop to show a string when the spinbutton has no value (i.e. placeholder="--").

Min, max, and step

Spinbuttons have a default range from 1 to 100, which can be changed by setting the min and max props. The default step increment is 1, and can be changed via the step prop (decimal values allowed).

When step is set, the value will always be a multiple of the step size plus the minimum value.

<template>
  <div>
    <label for="sb-step">Spin button with step of 0.25</label>
    <b-form-spinbutton
      id="sb-step"
      v-model="value"
      min="0"
      max="10"
      step="0.25"
    ></b-form-spinbutton>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        value: 0
      }
    }
  }
</script>

<!-- b-form-spinbutton-step.vue -->

Number wrapping

By default, when the value is increased to the max value, it pressing the increment button will have no effect. Similarly when the value is as the min value, pressing the decrement button will have no effect.

To allow the spin button to wrap from max to min when incrementing (or min to max when decrementing), set the wrap prop to true.

<template>
  <div>
    <label for="sb-wrap">Wrapping value spin button</label>
    <b-form-spinbutton id="sb-wrap" wrap min="1" max="25" placeholder="--"></b-form-spinbutton>
  </div>
</template>

<!-- b-form-spinbutton-wrap.vue -->

Styling

Size

As with other form controls, <b-form-spinbutton> supports small and large sizing via setting the size prop to either 'sm' or 'lg', respectively.

<template>
  <div>
    <label for="sb-small">Spin button - Small size</label>
    <b-form-spinbutton id="sb-small" size="sm" placeholder="--" class="mb-2"></b-form-spinbutton>

    <label for="sb-default">Spin button - Default size</label>
    <b-form-spinbutton id="sb-default" placeholder="--" class="mb-2"></b-form-spinbutton>

    <label for="sb-large">Spin button - Large size</label>
    <b-form-spinbutton id="sb-large" size="lg" placeholder="--" class="mb-2"></b-form-spinbutton>
  </div>
</template>

<!-- b-form-spinbutton-size.vue -->

Inline

<template>
  <div>
    <label for="sb-inline">Inline spin button</label>
    <b-form-spinbutton id="sb-inline" v-model="value" inline></b-form-spinbutton>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        value: 50
      }
    }
  }
</script>

<!-- b-form-spinbutton-inline.vue -->

The spin button will automatically adjust it's width to fit the displayed value. See the Width section below for details on controlling or setting the width.

Vertical

Spinbuttons can be oriented in vertical mode:

<template>
  <div>
    <label for="sb-vertical">Vertical spin button</label><br>
    <b-form-spinbutton id="sb-vertical" v-model="value" vertical></b-form-spinbutton>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        value: 50
      }
    }
  }
</script>

<!-- b-form-spinbutton-vertical.vue -->

Vertical spin buttons can also be sized using the <code>size</code> prop. When in vertical mode, the spin button is rendered as an inline element.

The spin button will automatically adjust it's width to fit the displayed value. See the Width section below for details on controlling or setting the width.

Width

The control (when not vertical or inline) will expand to the maximum width of the parent container You can control width via utility classes such as w-25, w-50, w-75, or use styles to set the width.

When either vertical or inline is set, the control will adjust its width based on the displayed value. You can use css style to control the overall width of the control (i.e. style="width: 10rem;).

Number formatting and locale

By default <b-form-spinbutton> will format the displayed number in the users browser default locale. You can change the localized formatting by specifying a locale (or array of locales) via the locale prop. Number format localization is performed via <code>Intl.NumberFormat</code>. The locales available will be dependent on the browser implementation. Localization only controls the presentation of the value to the user, and does not affect the v-model.

<template>
  <div>
    <label for="sb-locales">Locale</label>
    <b-form-select id="sb-locales" v-model="locale" :options="locales"></b-form-select>
    <label for="sb-local" class="mt-2">Spin button with locale</label>
    <b-form-spinbutton
      id="sb-locale"
      v-model="value"
      :locale="locale"
      min="0"
      max="10"
      step="0.125"
    ></b-form-spinbutton>
    <p>Value: {{ value }}</p>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        value: 0,
        locale: 'fr-CA',
        locales: [
          { value: 'en', text: 'English' },
          { value: 'de', text: 'German' },
          { value: 'fr-CA', text: 'French (Canadian)' },
          { value: 'fa', text: 'Persian' },
          { value: 'ar-EG', text: 'Arabic (Egyptian)' }
        ]
      }
    }
  }
</script>

<!-- b-form-spinbutton-locale.vue -->

Alternatively, you can provide your own number formatter function to format the value displayed. This is useful for displaying text instead of a number, or if you want to implement different features of Intl.NumberFormat.

To provide a formatter function, set the prop formatter-fn to a method reference. The formatter is passed a single argument which is the current value. Note the formatter only affects the value displayed to the user and does not affect the v-model.

<template>
  <div>
    <label for="sb-days" class="mt-2">Spin button with formatter</label>
    <b-form-spinbutton
      id="sb-days"
      v-model="value"
      :formatter-fn="dayFormatter"
      min="0"
      max="6"
      wrap
    ></b-form-spinbutton>
    <p>Value: {{ value }}</p>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        value: 0,
        days: ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']
      }
    },
    methods: {
      dayFormatter(value) {
        return this.days[value]
      }
    }
  }
</script>

<!-- b-form-spinbutton-formatter.vue -->

Disabled and readonly states

Setting the prop disabled places the component in a disabled, non-interactive state. The readonly prop places the component in a readonly state (focusable, but the value cannot be changed by the user).

<template>
  <b-row>
    <b-col md="6" class="mb-2">
      <label for="sb-disabled">Disabled spin button</label>
      <b-form-spinbutton id="sb-disabled" v-model="value" disabled></b-form-spinbutton>
    </b-col>
    <b-col md="6" class="mb-2">
      <label for="sb-readonly" class="">Readonly spin button</label>
      <b-form-spinbutton id="sb-readonly" v-model="value" readonly></b-form-spinbutton>
    </b-col>
  </b-row>
</template>

<script>
  export default {
    data() {
      return {
        value: 50
      }
    }
  }
</script>

<!-- b-form-spinbutton-disabled-readonly.vue -->

Disabled spinbuttons will not be submitted during native browser form submission, while a readonly spinbutton will be submitted (as long as a name has been set via the name prop).

Validation states

When you default to a null value, and the user has not selected a value, you can use the state prop to apply one of the contextual validation styles to the component.

• true applies the valid styling to the component
• false applies the invalid styling to the component
• null applies no contextual styling (the default)

Required prop

Note that the required prop only generates the aria-required="true" attribute on the component, and does not perform any validation on form submit. You must validate the v-model in your application logic.

Note that if the prop required is set, and the v-model is null, the attribute aria-invalid="true" will be rendered on the component.

Events

The input event is used to update the v-model and is emitted any time the value changes.

The change event is emitted once the user releases the mouse button (when pressing the increment or decrement buttons) or when the user releases the ArrowDown or ArrowUp key. This can be handy when you need to debounce the input.

The following example illustrates the difference between the input and change events. Click and hold the increment or decrement button (or use the up/down arrow keys).

<template>
  <div>
    <label for="sb-input">Spin button - input and change events</label>
    <b-form-spinbutton
      id="sb-input"
      v-model="value1"
      @change="value2 = $event"
      wrap
    ></b-form-spinbutton>
    <p>Input event: {{ value1 }}</p>
    <p>Change event: {{ value2 }}</p>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        value1: 0,
        value2: null
      }
    }
  }
</script>

<!-- b-form-spinbutton-events.vue -->

Accessibility

The following keyboard controls are available when the spin button is focused:

• Home Sets the value to the min value
• End Sets the value to the max value
• ArrowUp Increases the value by the step amount
• ArrowDown Decreases the value by the step amount
• PageUp Increases the value by the step amount times the repeat-step-multiplier amount
• PageDown Decreases the value by the step amount times the repeat-step-multiplier amount

Pressing an holding the ArrowUp, ArrowDown, PageUp, or PageDown keys will auto-repeat the increment or decrement (after an initial delay). Holding down the ArrowUp or ArrowDown keys for an extended period will multiply the increment or decrement amount by the repeat-step-multiplier amount.

Note the the repeat-delay, repeat-threshold and repeat-interval only applies to the ArrowUp or ArrowDown keys.

Implementation notes

<b-form-spinbutton> uses a mixture of Bootstrap v4 utility classes (border, alignment, flex), form-control and button classes, along with additional custom BootstrapVue SCSS/CSS.

See also

• Range type input