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File input

The file input uses HTML's native file input. It allows users to select files from their device for upload. In addition to native input features, it adds support for:

  • Drag and drop
  • Clearing the input
  • Repopulating from an array
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Array value

The value of the file type should always be an array of objects where each object contains a name (string) and optional file (File) property. When selecting new files from a user’s device, FormKit will convert the native FileList to the required array-based structure automatically.

This structure can be used to pre-populate a file input with previously uploaded file values:

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Display only
Pre-populating an input with file names is for display purposes only. It’s an optional feature that provides a consistent interface to convey that a file was previously uploaded — however — a FileList is not attached to the actual <input> tag for upload.

Uploading files

The file upload process is left to your form’s submission handler. When submitting the form via full page request no further processing is necessary, however when submitting via XHR/Fetch request you will need to create an instance of FormData with the files attached. Here is a working example:

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The file input has no unique props but the native HTML input does have a number of unique attributes that alter the behavior of the file uploader.

Prop Type Default Description
Commonly used native attributes
accept -- -- View on MDN
capture -- -- View on MDN
multiple -- -- View on MDN
webkitdirectory -- -- View on MDN
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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.
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.
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.
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.

Section keys

You can target a specific section of an input using that section's "key". Read more about sections here.

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          Section-key Description
          fileListA wrapper for the whole list of files.
          fileItemAn element containing the fileName and remove action for each file.
          fileNameThe element containing the name of a file.
          removeFilesThe element that removes a file from the list.
          noFilesThe element shown when there are no files selected.
          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.
          innerA wrapper around the actual input element.
          suffixHas no output by default, but allows content directly after an input element.
          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.