A lightweight wrapper for common FileReader usage.

npm install file-reader-wrapper@0.9.10



A small library independant wrapper for the JavaScript FileReader interface.

This plugin is open source under the MIT License. It was developed in conjunction with a CSS sprite generator project:



FileReaderJS.setupInput(document.getElementById('file-input'), opts);
FileReaderJS.setupDrop(document.getElementById('dropzone'), opts);
FileReaderJS.setupClipboard(document.body, opts);

If you have jQuery:

$("#file-input, #dropzone").fileReaderJS(opts);


Use the FileReaderSync object when available to load the files in a separate worker. false by default. This will cause only the load or error events to fire (there will be none of the other ProgressEvents, as the operation is synchronous).


readAsMap: A collection taking key as a string that will be matched with regex against
    file types and the type to read as.  If no match is found, it will use readAsDefault.
    The default map is:
        'image/*': 'DataURL',
        'text/*' : 'Text'
readAsDefault: 'ArrayBuffer' | 'Text' | 'DataURL' (default)
accept: A regex string to match the contenttype of a given file.
        For example: 'image/*' to only accept images.
        on.skip will be called when a file does not match the filter.
dragClass: A CSS class to add onto the element called with setupDrop while dragging
    loadstart: function(e, file) { }
    progress: function(e, file) { }
    load: function(e, file) { }
    abort: function(e, file) { }
    error: function(e, file) { }
    loadend: function(e, file) { }
    beforestart: function(file) { } Called before a file is passed to the FileReader.  Return false to prevent processing.  This is used along with the 'accept' parameter to skip a file (ex: an image is too big to process).  This wouldn't be needed, except that Chrome sometimes crashes when calling abort():
    skip: function(file) { } Called only when a read has been skipped because of the accept string
    groupstart: function(group) { }
    groupend: function(group) { }

Parameters to events:

e - the native ProgressEvent created by the FileReader

file - an extension of the original File object.  See W3 link above for all native parameters.  Here are the extra fields

file.extra = {
    fileID: a generated int id for this file.
    groupID: the group that it belongs to
    nameNoExtension: 'myImage' instead of 'myImage.png'
    extension: 'png' instead of 'myImage.png'
    prettySize: '46.47' kb instead of 47585 (size field)

group: simple grouping of files.  Each time a change event or drop even happens and a FileList is created, and all of these files are stored inside a group object.

    groupID: a generated int id for this group
    files: the FileList associated with the group
    started: the Date the group was recieved as input
    ended: the Date all files in the group finished loading

Any contributions are welcome. Author: Brian Grinstead.