Upload File to Show Only Some File Format Instead of All Files Ruby
<input type="file">
<input> элемент с атрибутом type="file" позволяет пользователю выбрать один файл или более из файлового хранилища своего устройства. После выбора эти файлы могут быть загружены на сервер при помощи формы, или обработаны JavaScript и File API.
<input proper noun = "myFile" type = "file" > Value
Атрибут value элемента input содержит DOMString, который представляет путь к выбранным файлам. Если пользователь выбрал несколько файлов, value представляет первый файл из списка. Остальные файлы можно определить используя HTMLInputElement.files свойство элемента input.
Note:
- Если выбрано несколько файлов, строка представляет собой первый выбранный файл. JavaScript предоставляет доступ к остальным файлам через свойство
FileList. - Если не выбрано ни одного файла, .строка равна
""(пустая). - Строка начинается с
C:\fakepath\, для предотвращения определения файловой структуры пользователя вредоносным ПО.
Additional attributes
In add-on to the common attributes shared by all <input> elements, inputs of type file also support:
-
files - A
FileListobject that lists every selected file. This listing has no more than one member unless themultipleattribute is specified.
Using file inputs
A basic example
<form method = "mail" enctype = "multipart/form-data" > <div > <characterization for = "file" > Choose file to upload </characterization > <input type = "file" id = "file" proper noun = "file" multiple > </div > <div > <button > Submit </button > </div > </class > This produces the following output:
Regardless of the user'south device or operating organization, the file input provides a push button that opens upwardly a file picker dialog that allows the user to choose a file.
Including the multiple aspect, every bit shown above, specifies that multiple files can exist chosen at once. The user can choose multiple files from the file picker in whatsoever way that their chosen platform allows (eastward.1000. by holding down Shift or Control, and and then clicking). If yous only want the user to choose a single file per <input>, omit the multiple attribute.
When the form is submitted, each selected file'due south name volition be added to URL parameters in the post-obit manner: ?file=file1.txt&file=file2.txt
Getting data on selected files
The selected files' are returned past the element'due south files property, which is a FileList object containing a list of File objects. The FileList behaves like an array, so you can check its length holding to get the number of selected files.
Each File object contains the post-obit information:
-
name - The file's name.
-
lastModified - A number specifying the date and fourth dimension at which the file was last modified, in milliseconds since the UNIX epoch (January 1, 1970 at midnight).
-
lastModifiedDate - A
Appointmentobject representing the date and time at which the file was last modified. This is deprecated and should not be used. UtiliselastModifiedinstead. -
size - The size of the file in bytes.
-
type - The file's MIME blazon.
- webkitRelativePath
- A string specifying the file'southward path relative to the base of operations directory selected in a directory picker (that is, a
filepicker in which thewebkitdirectoryattribute is set). This is non-standard and should be used with caution.
Note: Yous can set as well equally go the value of HTMLInputElement.files in all modern browsers; this was most recently added to Firefox, in version 57 (come across баг 1384030).
Limiting accepted file types
Ofttimes you won't desire the user to be able to pick any capricious type of file; instead, y'all frequently desire them to select files of a specific type or types. For case, if your file input lets users upload a profile moving picture, you probably desire them to select web-uniform image formats, such as JPEG or PNG.
Acceptable file types tin can be specified with the accept attribute, which takes a comma-separated list of allowed file extensions or MIME types. Some examples:
-
accept="image/png"oraccept=".png"— Accepts PNG files. -
accept="paradigm/png, epitome/jpeg"oraccept=".png, .jpg, .jpeg"— Take PNG or JPEG files. -
accept="image/*"— Accept any file with animage/*MIME blazon. (Many mobile devices also allow the user have a picture with the camera when this is used.) -
take=".md,.docx,.xml,awarding/msword,application/vnd.openxmlformats-officedocument.wordprocessingml.document"— take annihilation that smells similar an MS Give-and-take certificate.
Let's expect like a more consummate instance:
<form method = "post" enctype = "multipart/grade-information" > <div > <label for = "profile_pic" > Choose file to upload </label > <input blazon = "file" id = "profile_pic" name = "profile_pic" accept = ".jpg, .jpeg, .png" > </div > <div > <button > Submit </button > </div > </form > This produces a similar-looking output to the previous example:
It may expect similar, just if you endeavour selecting a file with this input, you'll come across that the file picker only lets you lot select the file types specified in the accept value (the verbal nature differs across browsers and operating systems).
The accept aspect doesn't validate the types of the selected files; it simply provides hints for browsers to guide users towards selecting the right file types. It is nevertheless possible (in most cases) for users to toggle an selection in the file chooser that makes it possible to override this and select any file they wish, and and then choose incorrect file types.
Because of this, you should make sure that the accept aspect is backed up past appropriate server-side validation.
Examples
In this instance, nosotros'll present a slightly more advanced file chooser that takes advantage of the file information bachelor in the HTMLInputElement.files property, as well equally showing off a few clever tricks.
Notation: You can see the consummate source code for this example on GitHub — file-example.html (see it alive also). We won't explicate the CSS; the JavaScript is the chief focus.
Offset of all, permit'south look at the HTML:
<course method = "postal service" enctype = "multipart/grade-data" > <div > <label for = "image_uploads" > Choose images to upload (PNG, JPG) </label > <input blazon = "file" id = "image_uploads" name = "image_uploads" accept = ".jpg, .jpeg, .png" multiple > </div > <div class = "preview" > <p > No files currently selected for upload </p > </div > <div > <push button > Submit </button > </div > </grade > This is similar to what nosotros've seen before — goose egg special to comment on.
Next, let's walk through the JavaScript.
In the commencement lines of script, we get references to the course input itself, and the <div> element with the class of .preview. Side by side, we hibernate the <input> element — nosotros do this because file inputs tend to be ugly, difficult to style, and inconsistent in their design beyond browsers. You tin activate the input element by clicking its <characterization>, so it is amend to visually hide the input and style the label like a button, and then the user volition know to collaborate with it if they desire to upload files.
var input = document. querySelector ( 'input' ) ; var preview = document. querySelector ( '.preview' ) ; input.manner.opacity = 0 ; Annotation: opacity is used to hide the file input instead of visibility: hidden or brandish: none, because assistive applied science interprets the latter two styles to mean the file input isn't interactive.
Next, we add an event listener to the input to heed for changes to its selected value changes (in this case, when files are selected). The event listener invokes our custom updateImageDisplay() function.
input. addEventListener ( 'alter' , updateImageDisplay) ; Whenever the updateImageDisplay() function is invoked, we:
- Use a
whileloop to empty the previous contents of the preview<div>. - Grab the
FileListobject that contains the data on all the selected files, and store it in a variable calledcurFiles. - Check to meet if no files were selected, past checking if
curFiles.lengthis equal to 0. If so, print a message into the preview<div>stating that no files take been selected. - If files take been selected, we loop through each one, press information most it into the preview
<div>. Things to note here: - We use the custom
validFileType()role to check whether the file is of the right type (e.k. the image types specified in theacceptattribute). - If information technology is, we:
- Impress out its name and file size into a list item within the previous
<div>(obtained fromcurFiles[i].proper nounandcurFiles[i].size). The customreturnFileSize()function returns a nicely-formatted version of the size in bytes/KB/MB (by default the browser reports the size in absolute bytes). - Generate a thumbnail preview of the image past calling
window.URL.createObjectURL(curFiles[i])and reducing the image size in the CSS, so insert that image into the list item too.
- Impress out its name and file size into a list item within the previous
- If the file type is invalid, we display a message inside a list detail telling the user that they need to select a unlike file blazon.
office updateImageDisplay ( ) { while (preview.firstChild) { preview. removeChild (preview.firstChild) ; } var curFiles = input.files; if (curFiles.length === 0 ) { var para = certificate. createElement ( 'p' ) ; para.textContent = 'No files currently selected for upload' ; preview. appendChild (para) ; } else { var list = certificate. createElement ( 'ol' ) ; preview. appendChild (list) ; for ( var i = 0 ; i < curFiles.length; i++ ) { var listItem = certificate. createElement ( 'li' ) ; var para = document. createElement ( 'p' ) ; if ( validFileType (curFiles[i] ) ) { para.textContent = 'File proper noun ' + curFiles[i] .name + ', file size ' + returnFileSize (curFiles[i] .size) + '.' ; var image = certificate. createElement ( 'img' ) ; image.src = window. URL . createObjectURL (curFiles[i] ) ; listItem. appendChild (epitome) ; listItem. appendChild (para) ; } else { para.textContent = 'File name ' + curFiles[i] .proper noun + ': Not a valid file type. Update your selection.' ; listItem. appendChild (para) ; } list. appendChild (listItem) ; } } } The custom validFileType() part takes a File object as a parameter, then loops through the list of allowed file types, checking if whatever matches the file's type property. If a friction match is institute, the function returns true. If no lucifer is constitute, information technology returns fake.
var fileTypes = [ 'image/jpeg' , 'image/pjpeg' , 'image/png' ] part validFileType ( file ) { for ( var i = 0 ; i < fileTypes.length; i++ ) { if (file.type === fileTypes[i] ) { return true ; } } return false ; } The returnFileSize() role takes a number (of bytes, taken from the current file's size belongings), and turns information technology into a nicely formatted size in bytes/KB/MB.
function returnFileSize ( number ) { if (number < 1024 ) { return number + 'bytes' ; } else if (number > 1024 && number < 1048576 ) { return (number/ 1024 ) . toFixed ( one ) + 'KB' ; } else if (number > 1048576 ) { return (number/ 1048576 ) . toFixed ( 1 ) + 'MB' ; } } The instance looks like this; have a play:
Specifications
Browser compatibility
BCD tables only load in the browser
See likewise
- Using files from spider web applications — contains a number of other useful examples related to
<input blazon="file">and the File API.
Source: https://developer.mozilla.org/ru/docs/Web/HTML/Element/Input/file
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