🖼 A simple file-upload utility that shows a preview of the uploaded image. Written in pure JavaScript. No dependencies. Works well with Bootstrap 4 or without a framework.
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file-upload-with-preview

This is a simple frontend utility to help the file-upload process on your website. It is written in pure JavaScript, has no dependencies, and is a small 13.55 kB (gzipped). You can check out the live demo here.

For the most part, browsers do a good job of handling image-uploads. That being said - we find that the ability to show our users a preview of their upload can go a long way in increasing the confidence in their upload.

file-upload-with-preview aims to address the issue of showing a preview of a user's uploaded image in a simple to use package.

Features

  • Shows the actual image preview in the case of a single uploaded .jpg, .jpeg, .gif, or .png image. Shows a success-image in the case of an uploaded .pdf file, uploaded video, or other unrenderable file - so the user knows their image was collected successfully. In the case of multiple selected files, the user's selected images will be shown in a grid.
  • Shows the image name in the input bar. Shows the count of selected images in the case of multiple selections within the same input.
  • Allows the user to clear their upload, and clear individual images in the multiple grid.
  • Looks great - styling based on Bootstrap 4's custom file-upload style.
  • Framework agnostic - to access the uploaded file/files just use the cachedFileArray (always will be an array) property of your FileUploadWithPreview object.
  • For every file-group you want just initialize another FileUploadWithPreview object with its own uniqueId - this way you can have multiple file-uploads on the same page. You also can just use a single input designated with a multiple property to allow multiple files on the same input.

Installation

# npm
npm i file-upload-with-preview

# yarn
yarn add file-upload-with-preview

Or you can include it through the browser at the bottom of your page:

<script src="https://unpkg.com/file-upload-with-preview"></script>

Usage

When installed through npm or yarn:

// using require
const FileUploadWithPreview = require('file-upload-with-preview')

// using import
import FileUploadWithPreview from 'file-upload-with-preview'

// initialize a new FileUploadWithPreview object
const upload = new FileUploadWithPreview('myUniqueUploadId')

...or through the browser:

<script>
    var upload = new FileUploadWithPreview('myUniqueUploadId')
</script>

You'll also want to include the css in your <head></head>:

// JavaScript
import 'file-upload-with-preview/dist/file-upload-with-preview.min.css'
<!-- Browser -->
<link rel="stylesheet" type="text/css" href="https://unpkg.com/file-upload-with-preview/dist/file-upload-with-preview.min.css">

The JavaScript looks for a specific set of HTML elements to display the file input, label, image preview, and clear-button. Make sure to populate the custom-file-container element with the uniqueId:

<div class="custom-file-container" data-upload-id="myFirstImage">
    <label>Upload File <a href="javascript:void(0)" class="custom-file-container__image-clear" title="Clear Image">&times;</a></label>
    <label class="custom-file-container__custom-file" >
        <input type="file" class="custom-file-container__custom-file__custom-file-input" accept="*" multiple>
        <input type="hidden" name="MAX_FILE_SIZE" value="10485760" />
        <span class="custom-file-container__custom-file__custom-file-control"></span>
    </label>
    <div class="custom-file-container__image-preview"></div>
</div>

Then when you're ready to use the user's file for an API call or whatever, just access the user's uploaded file/files in the cachedFileArray property of your initialized object like this:

upload.cachedFileArray

You can optionally trigger image browser and clear selected images by script code:

upload.selectImage(); // to open image browser
upload.clearPreviewImage(); // clear all selected images

You may also want to capture the event that an image is selected:

window.addEventListener('fileUploadWithPreview:imageSelected', function(e) {
    // e.detail.uploadId
    // e.detail.cachedFileArray
    // e.detail.selectedFilesCount
    // Use e.detail.uploadId to match up to your specific input
    if (e.detail.uploadId === 'mySecondImage') {
        console.log(e.detail.cachedFileArray)
        console.log(e.detail.selectedFilesCount)
    }
})

Note

The cachedFileArray property is always an array. So if you are only allowing the user to upload a single file, you can access that file at cachedFileArray[0] - otherwise just send the entire array to your backend to handle it normally.

Make sure to set multiple on your input if you want to allow the user to select multiple images.

Properties

name type description
uploadId String The id you set for the instance
options.showDeleteButtonOnImages Boolean Show a delete button on images in the grid. Default true
cachedFileArray Array The current selected files
selectedFilesCount Number The count of the currently selected files
el Element The main container for the instance
input Element The main container for the instance
inputLabel Element The label for the image name/count
imagePreview Element The display panel for the images
clearButton Element The button to reset the instance

Methods

method parameters description
selectImage none Open the image browser
clearPreviewImage none Clear the cachedFileArray

Events

event value description
fileUploadWithPreview:imageSelected e (e.detail.uploadId, e.detail.cachedFileArray, e.detail.selectedFilesCount) Triggered each time file/files are selected. Delivers the uploadId, updated cachedFilesArray, and selectedFilesCount for the event.
fileUploadWithPreview:imageDeleted e (e.detail.uploadId, e.detail.cachedFileArray, e.detail.selectedFilesCount) Triggered each time a file is deleted. Delivers the uploadId, updated cachedFilesArray, and selectedFilesCount for the event.

Full Example

<html>
    <head>
        ...
        <link rel="stylesheet" type="text/css" href="https://unpkg.com/file-upload-with-preview/dist/file-upload-with-preview.min.css">

        <!-- You'll want to make sure to at least set a width on the -->
        <!-- .custom-file-container class... -->
        ...
    </head>
    <body>

        ...

        <div class="custom-file-container" data-upload-id="myUniqueUploadId">
            <label>Upload File <a href="javascript:void(0)" class="custom-file-container__image-clear" title="Clear Image">&times;</a></label>

            <label class="custom-file-container__custom-file" >
                <input type="file" class="custom-file-container__custom-file__custom-file-input" accept="*" multiple>
                <input type="hidden" name="MAX_FILE_SIZE" value="10485760" />
                <span class="custom-file-container__custom-file__custom-file-control"></span>
            </label>
            <div class="custom-file-container__image-preview"></div>
        </div>

        ...

        <script src="https://unpkg.com/file-upload-with-preview"></script>
        <script>
            var upload = new FileUploadWithPreview('myUniqueUploadId')
        </script>

    </body>
</html>

In this example we set the MAX_FILE_SIZE value to 10485760 (10MB), the accepted images to * (everything), and designate multiple to allow the user to select multiple files - you can adjust those settings to whatever you like. For example, if you'd like to limit uploads to only images and pdf's and only allow a single file upload use the following:

<input type="file" class="custom-file-container__custom-file__custom-file-input" accept="application/pdf,image/*">
<input type="hidden" name="MAX_FILE_SIZE" value="10485760" />

Vue Example

View the Vue example on codesandbox:

Edit Vue Template

Testing

Use npm run test to run the tests.

Development

Clone the repo, then use the following to work on the project locally:

npm install

# watch changes
# (Open the index.html to work real-time. Refresh browser to test changes.)
npm run watch

# when done working
npm run build

Other

Go ahead and fork the project! Submit an issue if needed. Have fun!

License

Copywrite 2017 Promosis

MIT