退步青年

      function decodeUtf8(arrayBuffer) {
        var result = ''
        var i = 0
        var c = 0
        var c1 = 0
        var c2 = 0
        var c3 = 0

        var data = new Uint8Array(arrayBuffer)

        // If we have a BOM skip it
        if (data.length >= 3 && data[0] === 0xef && data[1] === 0xbb && data[2] === 0xbf) {
          i = 3
        }

        while (i < data.length) {
          c = data[i]

          if (c < 128) {
            result += String.fromCharCode(c)
            i++
          } else if (c > 191 && c < 224) {
            if (i + 1 >= data.length) {
              throw 'UTF-8 Decode failed. Two byte character was truncated.'
            }
            c2 = data[i + 1]
            result += String.fromCharCode(((c & 31) << 6) | (c2 & 63))
            i += 2
          } else {
            if (i + 2 >= data.length) {
              throw 'UTF-8 Decode failed. Multi byte character was truncated.'
            }
            c2 = data[i + 1]
            c3 = data[i + 2]
            result += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63))
            i += 3
          }
        }
        return result
      }