validation.js

var $ = uploadcare.jQuery

function fileTypeLimit(types) {
  types = types.split(' ')

  return function(fileInfo) {
    if (fileInfo.name === null) {
      return
    }
    var extension = fileInfo.name.split('.').pop()

    if (types.indexOf(extension) == -1) {
      throw new Error('fileType')
    }
  }
}

function fileSizeLimit(max) {
  return function(fileInfo) {
    if (fileInfo.size === null) {
      return
    }
    if (max && fileInfo.size > max) {
      throw new Error('fileMaximumSize')
    }
  }
}

$(document).ready(function($) {
  $('[role=uploadcare-uploader][data-file-types]').each(function() {
    var input = $(this)
    var widget = uploadcare.Widget(input)

    widget.validators.push(fileTypeLimit(input.data('fileTypes')))
  })
  $('[role=uploadcare-uploader][data-max-size]').each(function() {
    var input = $(this)
    var widget = uploadcare.Widget(input)

    widget.validators.push(fileSizeLimit(input.data('maxSize')))
  })
})
UPLOADCARE_LOCALE_TRANSLATIONS = {
  // messages for widget
  errors: {
    fileType: 'This type of file is not allowed.',
    fileMaximumSize: 'This file exceeds 1500mb',
  },
  // messages for dialog’s error page
  dialog: {
    tabs: {
      preview: {
        error: {
          fileType: {
            title: 'Oops, we dont accept that type of file.',
            text: 'Please make sure you are uploading either an MP4 JPG or PDF file.',
            back: 'Try Again',
          },
          fileMaximumSize: {
            title: 'Looks like your upload is too big.',
            text: 'Please ensure your file is no larger than 1500mb',
            back: 'Try Again',
          },
        },
      },
    },
  },
}