README.md
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
<code>File</code> 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
<code>File</code> object instances.
Directory mode
CAUTION: Directory mode is a non-standard feature. While being supported by all modern browsers, it should not be relied on for production. Read more on MDN and Can I use.
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
<code>File.webkitRelativePath</code>.
Directory mode is also supported when the file input is in <code>plain</code> 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 <code>plain</code> 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 <code>plain</code> 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 <code>plain</code> 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:
Argument | Type | Description |
---|---|---|
[1] files |
Array | Flat array of File objects |
[2] filesTraversed |
Array | Array of arrays of File objects when in <code>directory</code> mode |
[3] names |
Array | Flat array of file names (strings) |
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:
Property | Type | Description |
---|---|---|
files |
Array | Flat array of File objects |
filesTraversed |
Array | Array of arrays of File objects when in <code>directory</code> mode |
names |
Array | Flat array of file names (strings) |
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 formtrue
(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 fieldsnull
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 <code>plain</code> 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
<code>multiple</code>/<code>directory</code> 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 <code>directory</code> 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 <code>directory</code> 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.
<!-- Component reference added automatically from component package.json -->