ice.fo.utils/MediaUploadUtils.js

// Doc: https://stackoverflow.com/questions/18299806/how-to-check-file-mime-type-with-javascript-before-upload
export function getBLOBFileHeader (blob) {
  return new Promise((resolve) => {
    const fileReader = new FileReader()

    fileReader.onloadend = function (e) {
      const arr = (new Uint8Array(e.target.result)).subarray(0, 4)
      let header = ''
      for (let i = 0; i < arr.length; i++) {
        header += arr[i].toString(16)
      }

      const isValiddMime = checkValidMimeType(header)

      resolve(isValiddMime)
    }
    fileReader.readAsArrayBuffer(blob)
  })
}

function checkValidMimeType (headerString) {
  const validCode = ['89504e47', '47494638', 'ffd8ffe0', 'ffd8ffe1', 'ffd8ffe2', '66747970', '00014', '3026B275']
  return validCode.includes(headerString)
}