var source = new Uint8Array([0x32, 0x65, 0x42, 0x56]);
  var nativeEndian = new Uint16Array(new Uint8Array([0x12, 0x34]).buffer)[0] === 0x3412;
  
  var buf = new ArrayBuffer(16);
  var uint8 = new Uint8Array(buf);
  var int8 = new Int8Array(buf);
  var uint16 = new Uint16Array(buf);
  var int16 = new Int16Array(buf);
  var uint32 = new Uint32Array(buf);
  var int32 = new Int32Array(buf);
  var float32 = new Float32Array(buf);
  var float64 = new Float64Array(buf);
  
  function peek(bytes, littleEndian) {
    var i, _i, _j;
    if (littleEndian == null) {
      littleEndian = false;
    }
    if (littleEndian === nativeEndian) {
      for (i = _i = 0; _i < bytes; i = _i += 1) {
        uint8[i] = source[i];
      }
    } else {
      for (i = _j = 0; _j < bytes; i = _j += 1) {
        uint8[bytes - i - 1] = source[i];
      }
    }
  }
  
  function readUInt16_1(littleEndian) {
    peek(2, littleEndian);
    return uint16[0];
  }
  
  var buf2 = new ArrayBuffer(10);
  var uint8_2 = new Uint8Array(buf2);
  var view = new DataView(buf2);
  
  function peek2(bytes) {
    for (var i = 0; i < bytes; i++) {
      uint8_2[i] = source[i];
    }
  }
  
  function readUInt32_2(littleEndian) {
    peek2(4);
    return view.getUint32(0, littleEndian);
  }
  
  function readUInt32_3(littleEndian) {
    var a0 = source[0],
      a1 = source[1],
      a2 = source[2],
      a3 = source[3];
  
    if (littleEndian)
      return ((a3 << 24) >>> 0) + (a2 << 16) + (a1 << 8) + (a0);
    else
      return ((a0 << 24) >>> 0) + (a1 << 16) + (a2 << 8) + (a3);
  }
  
  function readUint16(littleEndian) {
    var a0 = source[0],
      a1 = source[1];
  
    if (littleEndian)
      return ((a1 << 8) >>> 0) + a0;
    else
      return ((a0 << 8) >>> 0) + a1;
  }

Teardown JS

Test cases

Test #1

Title *

Async

Code *readUInt16_1();

Test #2

Title *

Async

Code *readUInt32_2();

Test #3

Title *

Async

Code *readUint16();

Test case details

Preparation Code

Test cases

Test #1

Test #2

Test #3