Pro installation quickstart 🚀

Basic example

The dropdown input allows users to select a value from a customizable list of options:

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Defining options

The options prop can accept three different formats of values:

  • An array of objects with value and label keys (see example above)
  • An array of strings ['A', 'B', 'C']
  • An object literal with key-value pairs { a: 'A', b: 'B', c: 'C' }
  • A function that returns any of the above
Empty options

If you assign options as an empty array, the input will be rendered in a disabled state.

Empty message

The dropdown input, by default, will be rendered in a disabled state if no options are passed. Optionally, you may pass the empty-message prop a message to display when no options are available:

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Unlike native select elements, the dropdown input allows you to customize the options list with markup.

Option slot

The dropdown input allows you to customize the look and feel of each option by using the option slot. In this example, we are using the option slot to display each option's asset; logo and name:

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Selection slot

If you only want to customize the display of the selected option, use the selection slot:

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Loading options

Instead of passing a static list of options to the options prop, you can assign it to a function. Doing so is useful when you need to load options from an API or another source.

Single request

Let's say we had an API endpoint that returned all the options we needed for a given dropdown input. Here is an example of how we could write the dropdown input to load options from a single request:

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In the example above, we are assigning the options prop to the loadHorrorMovies function. After the request, we're iterating over the results to ensure that we return an array of objects with explicit value and label properties.

Multiple pages

What about loading options from an API where you need to be able to make multiple requests to perform pagination? When a function is set to the options prop it is passed FormKit node's context object as an argument. Within this context object are page and hasNextPage properties. The page property is the current page number, and the hasNextPage property is a function to be called when there are more pages to load:

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In the above example, we are calling hasNextPage when we determine there are more pages to load. When this is done, FormKit appends a Load more option at the end of the rendered options list and automatically increments its page property. When the user selects the Load more option, the function assigned to the options prop is called again, and the process repeats.

Option loader

Rehydrating values

FormKit's dropdown input also provides an optionLoader prop that allows you to rehydrate values that are not in the options list. In this example, we'll provide the autocomplete an initial value (a movie ID), and assign the optionLoader to a function that will make a request to the API to get the movie:

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Notice in the example above that the optionLoader function is passed two arguments: the value of the selected option (in this case, the movie ID) and the cachedOption. The cachedOption prop is used for preventing unnecessary lookups. If the cachedOption is not null it means that the selected option has already been loaded, and you can return the cachedOption directly.

Fetching additional data

Instead of using the optionLoader prop to rehydrate values that are not in the options list, you can use the optionLoader to perform a look-up to fetch additional data. In this example, after selecting an option, we are going to perform a look-up to load the selected option's movie review:

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Load on scroll

If you would rather allow the user to load more options without having to click the Load more option at the bottom of the options list, you can set the load-on-scroll prop to true, and our function, loadCurrentlyPopularMovies will be called again:

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Full example

Now let's combine what we've learned so far by leveraging the option slot for custom markup and setting the options prop to a function that will return pages of movies from an API:

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When using the dropdown with static options, FormKit's dropdown also comes with a unique feature called overscroll. In this example, we'll see what the behavior is when setting overscroll to true:

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Props & Attributes

optionsany[]The list of options the user can select from.
load-on-scrollbooleanfalseWhen set to `true`, the dropdown will try loading more options based on the end-user`s scroll position
option-loaderfunctionnullUsed for hydrating initial value, or performing an additional request to load more information of a selected option.
empty-messagestringundefinedRenders a message when there are no options to display.
Show universal props
configObject{}Configuration options to provide to the input’s node and any descendent node of this input.
delayNumber20Number of milliseconds to debounce an input’s value before the commit hook is dispatched.
dirtyBehaviorstringtouchedDetermines how the "dirty" flag of this input is set. Can be set to touched or comparetouched (the default) is more performant, but will not detect when the form is once again matching its initial state.
errorsArray[]Array of strings to show as error messages on this field.
helpString''Text for help text associated with the input.
idStringinput_{n}The unique id of the input. Providing an id also allows the input’s node to be globally accessed.
ignoreBooleanfalsePrevents an input from being included in any parent (group, list, form etc). Useful when using inputs for UI instead of actual values.
indexNumberundefinedAllows an input to be inserted at the given index if the parent is a list. If the input’s value is undefined, it inherits the value from that index position. If it has a value it inserts it into the lists’s values at the given index.
labelString''Text for the label element associated with the input.
nameStringinput_{n}The name of the input as identified in the data object. This should be unique within a group of fields.
parentFormKitNodecontextualBy default the parent is a wrapping group, list or form — but this props allows explicit assignment of the parent node.
prefix-iconString''Specifies an icon to put in the prefixIcon section.
preservebooleanfalsePreserves the value of the input on a parent group, list, or form when the input unmounts.
preserve-errorsbooleanfalseBy default errors set on inputs using setErrors are automatically cleared on input, setting this prop to true maintains the error until it is explicitly cleared.
sections-schemaObject{}An object of section keys and schema partial values, where each schema partial is applied to the respective section.
suffix-iconString''Specifies an icon to put in the suffixIcon section.
typeStringtextThe type of input to render from the library.
validationString, Array[]The validation rules to be applied to the input.
validation-visibilityStringblurDetermines when to show an input's failing validation rules. Valid values are blur, dirty, and live.
validation-labelString{label prop}Determines what label to use in validation error messages, by default it uses the label prop if available, otherwise it uses the name prop.
validation-rulesObject{}Additional custom validation rules to make available to the validation prop.
valueAnyundefinedSeeds the initial value of an input and/or its children. Not reactive. Can seed entire groups (forms) and lists..


You can target a specific section of an input using that section's "key", allowing you to modify that section's classes, HTML (via :sections-schema), or content (via slots). Read more about sections here.

Outer structure

View on a larger screen to see this section diagram.

Select t-shirt color
Blue Gray Tan
Turn sound effects on and off.
Something wrong happened.

Inner listbox structure

Below is the inner options list (listbox) structure from the diagram above:

View on a larger screen to see this section diagram.

selectorThe selector section is a button element that opens the dropdown options list.
selectionContains the selected option.
listitemA list item element that contains the option section.
optionA div that contains the option content.
listboxThe listbox section is a ul element that contains the options list.
dropdownWrapperWraps the listbox section. A div that handles scrolling the listbox.
optionLoadingA span element that is conditionally rendered within the selected option when loading is occurring.
loaderIconAn element for outputting an icon in the selector element when loading is occurring.
selectIconAn element for outputting an icon in the selector element when the dropdown is closed.
selectedIconAn element for outputting an icon next to the selected option when inside the listbox.
loadMoreA list item element that is conditionally rendered at the bottom of the options list when there are more pages to load.
loadMoreInnerA span element that acts as a wrapper for the loaderIcon within the loadMore section.
emptyMessageA list item element that is conditionally rendered when there are no options to display.
emptyMessageInnerA span element that acts as a wrapper for the emptyMessage section.
Show universal section keys
outerThe outermost wrapping element.
wrapperA wrapper around the label and input.
labelThe label of the input.
prefixHas no output by default, but allows content directly before an input element.
prefixIconAn element for outputting an icon before the prefix section.
innerA wrapper around the actual input element.
suffixHas no output by default, but allows content directly after an input element.
suffixIconAn element for outputting an icon after the suffix section.
inputThe input element itself.
helpThe element containing help text.
messagesA wrapper around all the messages.
messageThe element (or many elements) containing a message — most often validation and error messages.