Hash/checksum generation in client side JS

gistfile1.js

function createHexHash (algo, arrayBuffer, callback) {
  if (Object.prototype.toString.call(arrayBuffer) == '[object String]') {
    var encoder = new TextEncoder('utf-8')
    arrayBuffer = encoder.encode(arrayBuffer)
  }
  crypto.subtle.digest(algo, arrayBuffer).then(function (hash) {
    var hex = ""
    var array = new Uint8Array(hash)
    for (var i = 0; i < array.byteLength; i++) {
      var byte = array[i]
      var pad = ""
      if (byte < 16) pad = "0"
      hex += pad + byte.toString(16)
    }
    callback(hex)
  })
}