Form File

Customized, cross-browser consistent, file input control that supports single file, multiple files, and directory upload (for browsers that support directory mode).

<template>
  <div>
    <!-- Styled -->
    <b-form-file
      v-model="file1"
      :state="Boolean(file1)"
      placeholder="Choose a file or drop it here..."
      drop-placeholder="Drop file here..."
    ></b-form-file>
    <div class="mt-3">Selected file: {{ file1 ? file1.name : '' }}</div>

    <!-- Plain mode -->
    <b-form-file v-model="file2" class="mt-3" plain></b-form-file>
    <div class="mt-3">Selected file: {{ file2 ? file2.name : '' }}</div>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        file1: null,
        file2: null
      }
    }
  }
</script>

<!-- b-form-file.vue -->

For cross browser consistency, <b-form-file> defaults to the Bootstrap custom file input to replace the browser defaults. They're built on top of semantic and accessible markup, so it is a solid replacement for the default file input.

Single file (default)

On single file mode, when no file is selected or user cancels the "Browse" dialog, v-model is null indicating no file selected. When a file is selected the return value will be a JavaScript File object instance.

Multiple files

Multiple file uploading is supported by adding multiple prop to component. In this case v-model is always an Array. When no files are selected, an empty array will be returned. When a file or files are selected the return value will be an array of JavaScript File object instances.

Directory mode

By adding the directory prop, a user can select directories instead of files. When a directory is selected, the directory and its entire hierarchy of contents are included in the set of selected items.

When in directory mode, files are returned in a nested array format by default. i.e.

dirA/
  - fileA1
  - fileA2
  - dirB/
    - fileB1
  - dirC/
    - fileC1
    - fileC2
dirD/
  - fileD1

will be returned as (or similar, file/directory order may vary):

[[fileA1, fileA2, [fileB1], [fileC1, fileC2]], [fileD1]]

If you set the no-traverse prop, the array will be flattened:

[fileA1, fileA2, fileB1, fileC1, fileC2, fileD1]

Each file entry will have a special $path prop that will contain the relative path of each file. For nested directory structures, BootstrapVue uses its own routine to determine the relative path, otherwise it relies on File.webkitRelativePath.

Directory mode is also supported when the file input is in plain mode on most modern browsers.

Drag and Drop support

Drop mode is enabled by default. It can disabled by setting the no-drop prop. no-drop has no effect in plain mode (some browsers support dropping files onto a plain input file).

You can optionally set a different placeholder while dragging via the drop-placeholder prop or the scoped drop-placeholder slot. The prop only supports plain text. Use the slot for custom HTML markup. The slot takes precedence over the prop. The drop-placeholder prop/slot has no effect if no-drop is set or in plain mode.

Note that native browser constraints (such as required) will not work with drop mode, as the hidden file input does not handle the drag and drop functionality and will have zero files selected.

Limiting to certain file types

You can limit the file types by setting the accept prop to a string containing the allowed file type(s). To specify more than one type, separate the values with a comma.

<div>
  <!-- Accept all image formats by IANA media type wildcard-->
  <b-form-file accept="image/*"></b-form-file>

  <!-- Accept specific image formats by IANA type -->
  <b-form-file accept="image/jpeg, image/png, image/gif"></b-form-file>

  <!-- Accept specific image formats by extension -->
  <b-form-file accept=".jpg, .png, .gif"></b-form-file>
</div>

To accept any file type, leave accept as null (default). You can mix and match IANA media types and extensions.

Refer to IANA Media Types for a complete list of standard media types.

Note: Not all browsers support or respect the accept attribute on file inputs.

For drag and drop, BootstrapVue uses an internal file type checking routine and will filter out files that do not have the correct IANA media type or extension.

Customizing

<b-form-file>, when not in plain mode, provides several features for customizing its appearance.

Control sizing

Use the size prop to control the visual size of the input. The default size is considered md (medium). Optional sizes are lg (large) and sm (small). These sizes line up with the sizes available on other form controls.

<div>
  <b-form-group label="Small:" label-cols-sm="2" label-size="sm">
    <b-form-file id="file-small" size="sm"></b-form-file>
  </b-form-group>

  <b-form-group label="Default:" label-cols-sm="2">
    <b-form-file id="file-default"></b-form-file>
  </b-form-group>

  <b-form-group label="Large:" label-cols-sm="2" label-size="lg">
    <b-form-file id="file-large" size="lg"></b-form-file>
  </b-form-group>
</div>

<!-- form-file-sizes.vue -->

Note: Bootstrap v4.x does not natively support sizes for the custom file control. However, BootstrapVue includes custom SCSS/CSS that adds support for sizing the custom file input control.

Customize the placeholder text

Use the placeholder prop or the scoped placeholder slot to change the prompt text that is shown when no files are selected. The prop only supports plain text. Use the slot for custom HTML markup. The slot takes precedence over the prop.

Customize browse button label

If you want to globally change Browse label, you can add something like this to your global stylesheets. Also it is advised to use :lang() for multi-language sites.

.custom-file-input:lang(en) ~ .custom-file-label::after {
  content: 'Browse';
}

Alternatively you can set the content of the custom file browse button text via the browse-text prop. Note, only plain text is supported. HTML and components are not supported.

File name formatter function

Set the prop file-name-formatter to a function that accepts three arguments:

The function should return a single formatted string (HTML is not supported). The formatter will not be called if no files are selected.

<template>
  <b-form-file multiple :file-name-formatter="formatNames"></b-form-file>
</template>

<script>
  export default {
    methods: {
      formatNames(files) {
        return files.length === 1 ? files[0].name : `${files.length} files selected`
      }
    }
  }
</script>

<!-- file-formatter-function.vue -->

File name formatting via scoped slot

Alternatively, you can use the scoped slot file-name to render the file names. The scoped slot will receive the following properties:

All three properties are always arrays, regardless of the setting of the multiple prop.

<template>
  <b-form-file multiple>
   <template slot="file-name" slot-scope="{ names }">
     <b-badge variant="dark">{{ names[0] }}</b-badge>
     <b-badge v-if="names.length > 1" variant="dark" class="ml-1">
       + {{ names.length - 1 }} More files
     </b-badge>
   </template>
  </b-form-file>
</template>

<!-- file-formatter-slot.vue -->

When using the file-name slot, the file-name-formatter prop is ignored. The slot will not be rendered when there are no file(s) selected.

Non custom file input

You can have <b-form-file> render a browser native file input by setting the plain prop. Note that many of the custom features do not apply when plain is set.

Contextual state feedback

Bootstrap includes validation styles for valid and invalid states on most form controls.

Generally speaking, you'll want to use a particular state for specific types of feedback:

• false (denotes invalid state) is great for when there's a blocking or required field. A user must fill in this field properly to submit the form
• true (denotes valid state) is ideal for situations when you have per-field validation throughout a form and want to encourage a user through the rest of the fields
• null displays no validation state (neither valid nor invalid)

To apply one of the contextual state icons on <b-form-file>, set the state prop to false (for invalid), true (for valid), or null (no validation state).

Note: Contextual states are not supported when in plain mode.

Autofocus

When the autofocus prop is set on <b-form-file>, the input will be auto-focused when it is inserted (i.e. mounted) into the document, or re-activated when inside a Vue <keep-alive> component. Note that this prop does not set the autofocus attribute on the input, nor can it tell when the input becomes visible.

Accessibility

When using the custom version of <b-form-file> input which hides the original input, it is highly recommended that you supply a document unique ID string via the id prop. This will automatically render the extra ARIA attributes required to improve usability for persons using assistive technologies.

Clearing the file selection

With inputs of type file, normally the v-model is uni-directional (meaning you cannot pre-set the selected files). However, you can clear the file input's selected files by setting the v-model to either null (for single mode) or an empty array [] (for multiple/directory mode).

Alternatively, <b-form-file> provides a reset() method that can be called to clear the file input. To take advantage of the reset() method, you will need to obtain a reference to the <b-form-file> component.

<template>
  <div>
    <b-form-file v-model="file" ref="file-input" class="mb-2"></b-form-file>

    <b-button @click="clearFiles" class="mr-2">Reset via method</b-button>
    <b-button @click="file = null">Reset via v-model</b-button>

    <p class="mt-2">Selected file: <b>{{ file ? file.name : '' }}</b></p>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        file: null
      }
    },
    methods: {
      clearFiles() {
        this.$refs['file-input'].reset()
      }
    }
  }
</script>

<!-- b-form-file-reset.vue -->

Implementation notes

As not all browsers allow setting a value of a file input (even to null or an empty string), b-form-input employs a technique that works cross-browser that involves changing the input type to null and then immediately back to type file.

Nested file structures in directory mode require Promise support in the browser. If targeting your app for older browsers, such as IE 11, please include a polyfill that provides Promise support. If Promise support is not detected, files will always be in a flat file structure.

Due to a "bug" in Chromium, nested file structures in directory mode are currently only supported when directories are dropped on the file input. When selecting them via the "Browse" dialog they will always be in a flattened array structure. Mozilla implemented the behavior the same way as Chromium.