web workers transferable objects

JavaScript performance comparison

Test case created by Samuel

Preparation code

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>

<script type="javascript/worker" id="workerFunc">
  var sevs = ['ERROR', 'INFO', 'WARN']

  function randomNumber(max){
    return Math.floor(Math.random()*max);
  } 
  function randomCharacter(){
    return String.fromCharCode(randomNumber(100));
  }
  function randomString(length){
   var str = "";
   for(var i = 0; i < length; ++i){
        str += randomCharacter();
   }
   return str;
  }

  function utf82ab(str) {
  var buf, bufView;
  buf = new ArrayBuffer(str.length);
  bufView = new Uint8Array(buf);
  for (var i=0, strLen=str.length; i<strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  };
  return buf;
};


  self.onmessage = function(e) {
    obj = {
      timestamp: +(new Date()), 
      severity: sevs[Math.floor(Math.random()*sevs.length)],
      category: randomString(50),
      thread: randomString(50),
      message: randomString(500)
    };
    if(e.data.method === 'full_stringified') {
      arr = []
      for(var i = 0; i < e.data.len; i++) {       
         arr.push(obj);
      }
      postMessage({method: e.data.method, result: JSON.stringify(arr)}); 
    } else if (e.data.method === 'iterative') {
      for(var i = 0; i < e.data.len; i++) {       
         postMessage({method: e.data.method, result: JSON.stringify(obj), len: e.data.len}); 
      }
    } else if (e.data.method === 'ab') {
      arr = []
      for(var i = 0; i < e.data.len; i++) {
        arr.push(obj); 
      }
      var ab = utf82ab(JSON.stringify(arr));
      postMessage(ab, [ab]); 
    }
  };
</script>

<script>
$(function() {
console.log("Creating web worker");

window.URL = window.URL || window.webkitURL || null;
var script = document.querySelector('#workerFunc');
var blob = new Blob([script.textContent]);
window.testWorker = new Worker(window.URL.createObjectURL(blob));

console.log("Setup complete");
});
</script>
      
<script>
Benchmark.prototype.setup = function() {
  "use strict";
  
  /*\
  |*|
  |*|  :: Number.isInteger() polyfill ::
  |*|
  |*|  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger
  |*|
  \*/
  
  if (!Number.isInteger) {
    Number.isInteger = function isInteger (nVal) {
      return typeof nVal === "number" && isFinite(nVal) && nVal > -9007199254740992 && nVal < 9007199254740992 && Math.floor(nVal) === nVal;
    };
  }
  
  /*\
  |*|
  |*|  StringView - Mozilla Developer Network - revision #6
  |*|
  |*|  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays/StringView
  |*|  https://developer.mozilla.org/User:fusionchess
  |*|
  |*|  This framework is released under the GNU Public License, version 3 or later.
  |*|  http://www.gnu.org/licenses/gpl-3.0-standalone.html
  |*|
  \*/
  
  function StringView (vInput, sEncoding /* optional (default: UTF-8) */, nOffset /* optional */, nLength /* optional */) {
  
    var fTAView, aWhole, aRaw, fPutOutptCode, fGetOutptChrSize, nInptLen, nStartIdx = isFinite(nOffset) ? nOffset : 0, nTranscrType = 15;
  
    if (sEncoding) { this.encoding = sEncoding.toString(); }
  
    encSwitch: switch (this.encoding) {
      case "UTF-8":
        fPutOutptCode = StringView.putUTF8CharCode;
        fGetOutptChrSize = StringView.getUTF8CharLength;
        fTAView = Uint8Array;
        break encSwitch;
      case "UTF-16":
        fPutOutptCode = StringView.putUTF16CharCode;
        fGetOutptChrSize = StringView.getUTF16CharLength;
        fTAView = Uint16Array;
        break encSwitch;
      case "UTF-32":
        fTAView = Uint32Array;
        nTranscrType &= 14;
        break encSwitch;
      default:
        /* case "ASCII", or case "BinaryString" or unknown cases */
        fTAView = Uint8Array;
        nTranscrType &= 14;
    }
  
    typeSwitch: switch (typeof vInput) {
      case "string":
        /* the input argument is a primitive string: a new buffer will be created. */
        nTranscrType &= 7;
        break typeSwitch;
      case "object":
        classSwitch: switch (vInput.constructor) {
          case StringView:
            /* the input argument is a stringView: a new buffer will be created. */
            nTranscrType &= 3;
            break typeSwitch;
          case String:
            /* the input argument is an objectified string: a new buffer will be created. */
            nTranscrType &= 7;
            break typeSwitch;
          case ArrayBuffer:
            /* the input argument is an arrayBuffer: the buffer will be shared. */
            aWhole = new fTAView(vInput);
            nInptLen = this.encoding === "UTF-32" ?
                vInput.byteLength >>> 2
              : this.encoding === "UTF-16" ?
                vInput.byteLength >>> 1
              :
                vInput.byteLength;
            aRaw = nStartIdx === 0 && (!isFinite(nLength) || nLength === nInptLen) ?
              aWhole
              : new fTAView(vInput, nStartIdx, !isFinite(nLength) ? nInptLen - nStartIdx : nLength);
  
            break typeSwitch;
          case Uint32Array:
          case Uint16Array:
          case Uint8Array:
            /* the input argument is a typedArray: the buffer, and possibly the array itself, will be shared. */
            fTAView = vInput.constructor;
            nInptLen = vInput.length;
            aWhole = vInput.byteOffset === 0 && vInput.length === (
              fTAView === Uint32Array ?
                vInput.buffer.byteLength >>> 2
              : fTAView === Uint16Array ?
                vInput.buffer.byteLength >>> 1
              :
                vInput.buffer.byteLength
            ) ? vInput : new fTAView(vInput.buffer);
            aRaw = nStartIdx === 0 && (!isFinite(nLength) || nLength === nInptLen) ?
              vInput
              : vInput.subarray(nStartIdx, isFinite(nLength) ? nStartIdx + nLength : nInptLen);
  
            break typeSwitch;
          default:
            /* the input argument is an array or another serializable object: a new typedArray will be created. */
            aWhole = new fTAView(vInput);
            nInptLen = aWhole.length;
            aRaw = nStartIdx === 0 && (!isFinite(nLength) || nLength === nInptLen) ?
              aWhole
              : aWhole.subarray(nStartIdx, isFinite(nLength) ? nStartIdx + nLength : nInptLen);
        }
        break typeSwitch;
      default:
        /* the input argument is a number, a boolean or a function: a new typedArray will be created. */
        aWhole = aRaw = new fTAView(Number(vInput) || 0);
  
    }
  
    if (nTranscrType < 8) {
  
      var vSource, nOutptLen, nCharStart, nCharEnd, nEndIdx, fGetInptChrSize, fGetInptChrCode;
  
      if (nTranscrType & 4) { /* input is string */
  
        vSource = vInput;
        nOutptLen = nInptLen = vSource.length;
        nTranscrType ^= this.encoding === "UTF-32" ? 0 : 2;
        /* ...or...: nTranscrType ^= Number(this.encoding !== "UTF-32") << 1; */
        nStartIdx = nCharStart = nOffset ? Math.max((nOutptLen + nOffset) % nOutptLen, 0) : 0;
        nEndIdx = nCharEnd = (Number.isInteger(nLength) ? Math.min(Math.max(nLength, 0) + nStartIdx, nOutptLen) : nOutptLen) - 1;
  
      } else { /* input is stringView */
  
        vSource = vInput.rawData;
        nInptLen = vInput.makeIndex();
        nStartIdx = nCharStart = nOffset ? Math.max((nInptLen + nOffset) % nInptLen, 0) : 0;
        nOutptLen = Number.isInteger(nLength) ? Math.min(Math.max(nLength, 0), nInptLen - nCharStart) : nInptLen;
        nEndIdx = nCharEnd = nOutptLen + nCharStart;
  
        if (vInput.encoding === "UTF-8") {
          fGetInptChrSize = StringView.getUTF8CharLength;
          fGetInptChrCode = StringView.loadUTF8CharCode;
        } else if (vInput.encoding === "UTF-16") {
          fGetInptChrSize = StringView.getUTF16CharLength;
          fGetInptChrCode = StringView.loadUTF16CharCode;
        } else {
          nTranscrType &= 1;
        }
  
      }
  
      if (nOutptLen === 0 || nTranscrType < 4 && vSource.encoding === this.encoding && nCharStart === 0 && nOutptLen === nInptLen) {
  
        /* the encoding is the same, the length too and the offset is 0... or the input is empty! */
  
        nTranscrType = 7;
  
      }
  
      conversionSwitch: switch (nTranscrType) {
  
        case 0:
  
        /* both the source and the new StringView have a fixed-length encoding... */
  
          aWhole = new fTAView(nOutptLen);
          for (var nOutptIdx = 0; nOutptIdx < nOutptLen; aWhole[nOutptIdx] = vSource[nStartIdx + nOutptIdx++]);
          break conversionSwitch;
  
        case 1:
  
        /* the source has a fixed-length encoding but the new StringView has a variable-length encoding... */
  
          /* mapping... */
  
          nOutptLen = 0;
  
          for (var nInptIdx = nStartIdx; nInptIdx < nEndIdx; nInptIdx++) {
            nOutptLen += fGetOutptChrSize(vSource[nInptIdx]);
          }
  
          aWhole = new fTAView(nOutptLen);
  
          /* transcription of the source... */
  
          for (var nInptIdx = nStartIdx, nOutptIdx = 0; nOutptIdx < nOutptLen; nInptIdx++) {
            nOutptIdx = fPutOutptCode(aWhole, vSource[nInptIdx], nOutptIdx);
          }
  
          break conversionSwitch;
  
        case 2:
  
        /* the source has a variable-length encoding but the new StringView has a fixed-length encoding... */
  
          /* mapping... */
  
          nStartIdx = 0;
  
          var nChrCode;
  
          for (nChrIdx = 0; nChrIdx < nCharStart; nChrIdx++) {
            nChrCode = fGetInptChrCode(vSource, nStartIdx);
            nStartIdx += fGetInptChrSize(nChrCode);
          }
  
          aWhole = new fTAView(nOutptLen);
  
          /* transcription of the source... */
  
          for (var nInptIdx = nStartIdx, nOutptIdx = 0; nOutptIdx < nOutptLen; nInptIdx += fGetInptChrSize(nChrCode), nOutptIdx++) {
            nChrCode = fGetInptChrCode(vSource, nInptIdx);
            aWhole[nOutptIdx] = nChrCode;
          }
  
          break conversionSwitch;
  
        case 3:
  
        /* both the source and the new StringView have a variable-length encoding... */
  
          /* mapping... */
  
          nOutptLen = 0;
  
          var nChrCode;
  
          for (var nChrIdx = 0, nInptIdx = 0; nChrIdx < nCharEnd; nInptIdx += fGetInptChrSize(nChrCode)) {
            nChrCode = fGetInptChrCode(vSource, nInptIdx);
            if (nChrIdx === nCharStart) { nStartIdx = nInptIdx; }
            if (++nChrIdx > nCharStart) { nOutptLen += fGetOutptChrSize(nChrCode); }
          }
  
          aWhole = new fTAView(nOutptLen);
  
          /* transcription... */
  
          for (var nInptIdx = nStartIdx, nOutptIdx = 0; nOutptIdx < nOutptLen; nInptIdx += fGetInptChrSize(nChrCode)) {
            nChrCode = fGetInptChrCode(vSource, nInptIdx);
            nOutptIdx = fPutOutptCode(aWhole, nChrCode, nOutptIdx);
          }
  
          break conversionSwitch;
  
        case 4:
  
        /* DOMString to ASCII or BinaryString or other unknown encodings */
  
          aWhole = new fTAView(nOutptLen);
  
          /* transcription... */
  
          for (var nIdx = 0; nIdx < nOutptLen; nIdx++) {
            aWhole[nIdx] = vSource.charCodeAt(nIdx) & 0xff;
          }
  
          break conversionSwitch;
  
        case 5:
  
        /* DOMString to UTF-8 or to UTF-16 */
  
          /* mapping... */
  
          nOutptLen = 0;
  
          for (var nMapIdx = 0; nMapIdx < nInptLen; nMapIdx++) {
            if (nMapIdx === nCharStart) { nStartIdx = nOutptLen; }
            nOutptLen += fGetOutptChrSize(vSource.charCodeAt(nMapIdx));
            if (nMapIdx === nCharEnd) { nEndIdx = nOutptLen; }
          }
  
          aWhole = new fTAView(nOutptLen);
  
          /* transcription... */
  
          for (var nOutptIdx = 0, nChrIdx = 0; nOutptIdx < nOutptLen; nChrIdx++) {
            nOutptIdx = fPutOutptCode(aWhole, vSource.charCodeAt(nChrIdx), nOutptIdx);
          }
  
          break conversionSwitch;
  
        case 6:
  
        /* DOMString to UTF-32 */
  
          aWhole = new fTAView(nOutptLen);
  
          /* transcription... */
  
          for (var nIdx = 0; nIdx < nOutptLen; nIdx++) {
            aWhole[nIdx] = vSource.charCodeAt(nIdx);
          }
  
          break conversionSwitch;
  
        case 7:
  
          aWhole = new fTAView(nOutptLen ? vSource : 0);
          break conversionSwitch;
  
      }
  
      aRaw = nTranscrType > 3 && (nStartIdx > 0 || nEndIdx < aWhole.length - 1) ? aWhole.subarray(nStartIdx, nEndIdx) : aWhole;
  
    }
  
    this.buffer = aWhole.buffer;
    this.bufferView = aWhole;
    this.rawData = aRaw;
  
    Object.freeze(this);
  
  }
  
  /* CONSTRUCTOR'S METHODS */
  
  StringView.loadUTF8CharCode = function (aChars, nIdx) {
  
    var nLen = aChars.length, nPart = aChars[nIdx];
  
    return nPart > 251 && nPart < 254 && nIdx + 5 < nLen ?
        /* (nPart - 252 << 32) is not possible in ECMAScript! So...: */
        /* six bytes */ (nPart - 252) * 1073741824 + (aChars[nIdx + 1] - 128 << 24) + (aChars[nIdx + 2] - 128 << 18) + (aChars[nIdx + 3] - 128 << 12) + (aChars[nIdx + 4] - 128 << 6) + aChars[nIdx + 5] - 128
      : nPart > 247 && nPart < 252 && nIdx + 4 < nLen ?
        /* five bytes */ (nPart - 248 << 24) + (aChars[nIdx + 1] - 128 << 18) + (aChars[nIdx + 2] - 128 << 12) + (aChars[nIdx + 3] - 128 << 6) + aChars[nIdx + 4] - 128
      : nPart > 239 && nPart < 248 && nIdx + 3 < nLen ?
        /* four bytes */(nPart - 240 << 18) + (aChars[nIdx + 1] - 128 << 12) + (aChars[nIdx + 2] - 128 << 6) + aChars[nIdx + 3] - 128
      : nPart > 223 && nPart < 240 && nIdx + 2 < nLen ?
        /* three bytes */ (nPart - 224 << 12) + (aChars[nIdx + 1] - 128 << 6) + aChars[nIdx + 2] - 128
      : nPart > 191 && nPart < 224 && nIdx + 1 < nLen ?
        /* two bytes */ (nPart - 192 << 6) + aChars[nIdx + 1] - 128
      :
        /* one byte */ nPart;
  
  };
  
  StringView.putUTF8CharCode = function (aTarget, nChar, nPutAt) {
  
    var nIdx = nPutAt;
  
    if (nChar < 0x80 /* 128 */) {
      /* one byte */
      aTarget[nIdx++] = nChar;
    } else if (nChar < 0x800 /* 2048 */) {
      /* two bytes */
      aTarget[nIdx++] = 0xc0 /* 192 */ + (nChar >>> 6);
      aTarget[nIdx++] = 0x80 /* 128 */ + (nChar & 0x3f /* 63 */);
    } else if (nChar < 0x10000 /* 65536 */) {
      /* three bytes */
      aTarget[nIdx++] = 0xe0 /* 224 */ + (nChar >>> 12);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 6) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + (nChar & 0x3f /* 63 */);
    } else if (nChar < 0x200000 /* 2097152 */) {
      /* four bytes */
      aTarget[nIdx++] = 0xf0 /* 240 */ + (nChar >>> 18);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 12) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 6) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + (nChar & 0x3f /* 63 */);
    } else if (nChar < 0x4000000 /* 67108864 */) {
      /* five bytes */
      aTarget[nIdx++] = 0xf8 /* 248 */ + (nChar >>> 24);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 18) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 12) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 6) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + (nChar & 0x3f /* 63 */);
    } else /* if (nChar <= 0x7fffffff) */ { /* 2147483647 */
      /* six bytes */
      aTarget[nIdx++] = 0xfc /* 252 */ + /* (nChar >>> 32) is not possible in ECMAScript! So...: */ (nChar / 1073741824);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 24) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 18) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 12) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + ((nChar >>> 6) & 0x3f /* 63 */);
      aTarget[nIdx++] = 0x80 /* 128 */ + (nChar & 0x3f /* 63 */);
    }
  
    return nIdx;
  
  };
  
  StringView.getUTF8CharLength = function (nChar) {
    return nChar < 0x80 ? 1 : nChar < 0x800 ? 2 : nChar < 0x10000 ? 3 : nChar < 0x200000 ? 4 : nChar < 0x4000000 ? 5 : 6;
  };
  
  StringView.loadUTF16CharCode = function (aChars, nIdx) {
  
    /* UTF-16 to DOMString decoding algorithm */
    var nFrstChr = aChars[nIdx];
  
    return nFrstChr > 0xD7BF /* 55231 */ && nIdx + 1 < aChars.length ?
      (nFrstChr - 0xD800 /* 55296 */ << 10) + aChars[nIdx + 1] + 0x2400 /* 9216 */
      : nFrstChr;
  
  };
  
  StringView.putUTF16CharCode = function (aTarget, nChar, nPutAt) {
  
    var nIdx = nPutAt;
  
    if (nChar < 0x10000 /* 65536 */) {
      /* one element */
      aTarget[nIdx++] = nChar;
    } else {
      /* two elements */
      aTarget[nIdx++] = 0xD7C0 /* 55232 */ + (nChar >>> 10);
      aTarget[nIdx++] = 0xDC00 /* 56320 */ + (nChar & 0x3FF /* 1023 */);
    }
  
    return nIdx;
  
  };
  
  StringView.getUTF16CharLength = function (nChar) {
    return nChar < 0x10000 ? 1 : 2;
  };
  
  /* Array of bytes to base64 string decoding */
  
  StringView.b64ToUint6 = function (nChr) {
  
    return nChr > 64 && nChr < 91 ?
        nChr - 65
      : nChr > 96 && nChr < 123 ?
        nChr - 71
      : nChr > 47 && nChr < 58 ?
        nChr + 4
      : nChr === 43 ?
        62
      : nChr === 47 ?
        63
      :
        0;
  
  };
  
  StringView.uint6ToB64 = function (nUint6) {
  
    return nUint6 < 26 ?
        nUint6 + 65
      : nUint6 < 52 ?
        nUint6 + 71
      : nUint6 < 62 ?
        nUint6 - 4
      : nUint6 === 62 ?
        43
      : nUint6 === 63 ?
        47
      :
        65;
  
  };
  
  /* Base64 string to array encoding */
  
  StringView.bytesToBase64 = function (aBytes) {
  
    var sB64Enc = "";
  
    for (var nMod3, nLen = aBytes.length, nUint24 = 0, nIdx = 0; nIdx < nLen; nIdx++) {
      nMod3 = nIdx % 3;
      if (nIdx > 0 && (nIdx * 4 / 3) % 76 === 0) { sB64Enc += "\r\n"; }
      nUint24 |= aBytes[nIdx] << (16 >>> nMod3 & 24);
      if (nMod3 === 2 || aBytes.length - nIdx === 1) {
        sB64Enc += String.fromCharCode(StringView.uint6ToB64(nUint24 >>> 18 & 63), StringView.uint6ToB64(nUint24 >>> 12 & 63), StringView.uint6ToB64(nUint24 >>> 6 & 63), StringView.uint6ToB64(nUint24 & 63));
        nUint24 = 0;
      }
    }
  
    return sB64Enc.replace(/A(?=A$|$)/g, "=");
  
  };
  
  
  StringView.base64ToBytes = function (sBase64, nBlockBytes) {
  
    var
      sB64Enc = sBase64.replace(/[^A-Za-z0-9\+\/]/g, ""), nInLen = sB64Enc.length,
      nOutLen = nBlockBytes ? Math.ceil((nInLen * 3 + 1 >>> 2) / nBlockBytes) * nBlockBytes : nInLen * 3 + 1 >>> 2, aBytes = new Uint8Array(nOutLen);
  
    for (var nMod3, nMod4, nUint24 = 0, nOutIdx = 0, nInIdx = 0; nInIdx < nInLen; nInIdx++) {
      nMod4 = nInIdx & 3;
      nUint24 |= StringView.b64ToUint6(sB64Enc.charCodeAt(nInIdx)) << 18 - 6 * nMod4;
      if (nMod4 === 3 || nInLen - nInIdx === 1) {
        for (nMod3 = 0; nMod3 < 3 && nOutIdx < nOutLen; nMod3++, nOutIdx++) {
          aBytes[nOutIdx] = nUint24 >>> (16 >>> nMod3 & 24) & 255;
        }
        nUint24 = 0;
      }
    }
  
    return aBytes;
  
  };
  
  StringView.makeFromBase64 = function (sB64Inpt, sEncoding, nByteOffset, nLength) {
  
    return new StringView(sEncoding === "UTF-16" || sEncoding === "UTF-32" ? StringView.base64ToBytes(sB64Inpt, sEncoding === "UTF-16" ? 2 : 4).buffer : StringView.base64ToBytes(sB64Inpt), sEncoding, nByteOffset, nLength);
  
  };
  
  /* DEFAULT VALUES */
  
  StringView.prototype.encoding = "UTF-8"; /* Default encoding... */
  
  /* INSTANCES' METHODS */
  
  StringView.prototype.makeIndex = function (nChrLength, nStartFrom) {
  
    var
  
      aTarget = this.rawData, nChrEnd, nRawLength = aTarget.length,
      nStartIdx = nStartFrom || 0, nIdxEnd = nStartIdx, nStopAtChr = isNaN(nChrLength) ? Infinity : nChrLength;
  
    if (nChrLength + 1 > aTarget.length) { throw new RangeError("StringView.prototype.makeIndex - The offset can\'t be major than the length of the array - 1."); }
  
    switch (this.encoding) {
  
      case "UTF-8":
  
        var nPart;
  
        for (nChrEnd = 0; nIdxEnd < nRawLength && nChrEnd < nStopAtChr; nChrEnd++) {
          nPart = aTarget[nIdxEnd];
          nIdxEnd += nPart > 251 && nPart < 254 && nIdxEnd + 5 < nRawLength ? 6
            : nPart > 247 && nPart < 252 && nIdxEnd + 4 < nRawLength ? 5
            : nPart > 239 && nPart < 248 && nIdxEnd + 3 < nRawLength ? 4
            : nPart > 223 && nPart < 240 && nIdxEnd + 2 < nRawLength ? 3
            : nPart > 191 && nPart < 224 && nIdxEnd + 1 < nRawLength ? 2
            : 1;
        }
  
        break;
  
      case "UTF-16":
  
        for (nChrEnd = nStartIdx; nIdxEnd < nRawLength && nChrEnd < nStopAtChr; nChrEnd++) {
          nIdxEnd += aTarget[nIdxEnd] > 0xD7BF /* 55231 */ && nIdxEnd + 1 < aTarget.length ? 2 : 1;
        }
  
        break;
  
      default:
  
        nIdxEnd = nChrEnd = isFinite(nChrLength) ? nChrLength : nRawLength - 1;
  
    }
  
    if (nChrLength) { return nIdxEnd; }
  
    return nChrEnd;
  
  };
  
  StringView.prototype.toBase64 = function (bWholeBuffer) {
  
    return StringView.bytesToBase64(
      bWholeBuffer ?
        (
          this.bufferView.constructor === Uint8Array ?
            this.bufferView
          :
            new Uint8Array(this.buffer)
        )
      : this.rawData.constructor === Uint8Array ?
        this.rawData
      :
        new Uint8Array(this.buffer, this.rawData.byteOffset, this.rawData.length << (this.rawData.constructor === Uint16Array ? 1 : 2))
      );
  
  };
  
  StringView.prototype.subview = function (nCharOffset /* optional */, nCharLength /* optional */) {
  
    var
  
      nChrLen, nCharStart, nStrLen, bVariableLen = this.encoding === "UTF-8" || this.encoding === "UTF-16",
      nStartOffset = nCharOffset, nStringLength, nRawLen = this.rawData.length;
  
    if (nRawLen === 0) {
      return new StringView(this.buffer, this.encoding);
    }
  
    nStringLength = bVariableLen ? this.makeIndex() : nRawLen;
    nCharStart = nCharOffset ? Math.max((nStringLength + nCharOffset) % nStringLength, 0) : 0;
    nStrLen = Number.isInteger(nCharLength) ? Math.max(nCharLength, 0) + nCharStart > nStringLength ? nStringLength - nCharStart : nCharLength : nStringLength;
  
    if (nCharStart === 0 && nStrLen === nStringLength) { return this; }
  
    if (bVariableLen) {
      nStartOffset = this.makeIndex(nCharStart);
      nChrLen = this.makeIndex(nStrLen, nStartOffset) - nStartOffset;
    } else {
      nStartOffset = nCharStart;
      nChrLen = nStrLen - nCharStart;
    }
  
    if (this.encoding === "UTF-16") {
      nStartOffset <<= 1;
    } else if (this.encoding === "UTF-32") {
      nStartOffset <<= 2;
    }
  
    return new StringView(this.buffer, this.encoding, nStartOffset, nChrLen);
  
  };
  
  StringView.prototype.forEachChar = function (fCallback, oThat, nChrOffset, nChrLen) {
  
    var aSource = this.rawData, nRawEnd, nRawIdx;
  
    if (this.encoding === "UTF-8" || this.encoding === "UTF-16") {
  
      var fGetInptChrSize, fGetInptChrCode;
  
      if (this.encoding === "UTF-8") {
        fGetInptChrSize = StringView.getUTF8CharLength;
        fGetInptChrCode = StringView.loadUTF8CharCode;
      } else if (this.encoding === "UTF-16") {
        fGetInptChrSize = StringView.getUTF16CharLength;
        fGetInptChrCode = StringView.loadUTF16CharCode;
      }
  
      nRawIdx = isFinite(nChrOffset) ? this.makeIndex(nChrOffset) : 0;
      nRawEnd = isFinite(nChrLen) ? this.makeIndex(nChrLen, nRawIdx) : aSource.length;
  
      for (var nChrCode, nChrIdx = 0; nRawIdx < nRawEnd; nChrIdx++) {
        nChrCode = fGetInptChrCode(aSource, nRawIdx);
        fCallback.call(oThat || null, nChrCode, nChrIdx, nRawIdx, aSource);
        nRawIdx += fGetInptChrSize(nChrCode);
      }
  
    } else {
  
      nRawIdx = isFinite(nChrOffset) ? nChrOffset : 0;
      nRawEnd = isFinite(nChrLen) ? nChrLen + nRawIdx : aSource.length;
  
      for (nRawIdx; nRawIdx < nRawEnd; nRawIdx++) {
        fCallback.call(oThat || null, aSource[nRawIdx], nRawIdx, nRawIdx, aSource);
      }
  
    }
  
  };
  
  StringView.prototype.valueOf = StringView.prototype.toString = function () {
  
    if (this.encoding !== "UTF-8" && this.encoding !== "UTF-16") {
      /* ASCII, UTF-32 or BinaryString to DOMString */
      return String.fromCharCode.apply(null, this.rawData);
    }
  
    var fGetCode, fGetIncr, sView = "";
  
    if (this.encoding === "UTF-8") {
      fGetIncr = StringView.getUTF8CharLength;
      fGetCode = StringView.loadUTF8CharCode;
    } else if (this.encoding === "UTF-16") {
      fGetIncr = StringView.getUTF16CharLength;
      fGetCode = StringView.loadUTF16CharCode;
    }
  
    for (var nChr, nLen = this.rawData.length, nIdx = 0; nIdx < nLen; nIdx += fGetIncr(nChr)) {
      nChr = fGetCode(this.rawData, nIdx);
      sView += String.fromCharCode(nChr);
    }
  
    return sView;
  
  };

};
</script>

Preparation code output

Test runner

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Java applet disabled.

Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
1k items in array
// async test
window.testWorker.onmessage = function(e) {
  (new StringView(e.data)).toString();
  deferred.resolve();
};
window.testWorker.postMessage({
  method: 'ab',
  len: 1000
});
pending…
10k items in array
// async test
window.testWorker.onmessage = function(e) {
    (new StringView(e.data)).toString();
  deferred.resolve();
};
window.testWorker.postMessage({
  method: 'ab',
  len: 10000
});
pending…
100k items in array
// async test
window.testWorker.onmessage = function(e) {
  (new StringView(e.data)).toString();
  deferred.resolve();
};
window.testWorker.postMessage({
  method: 'ab',
  len: 100000
});
pending…
500k items in array
// async test
window.testWorker.onmessage = function(e) {
  (new StringView(e.data)).toString();
  deferred.resolve();
};
window.testWorker.postMessage({
  method: 'ab',
  len: 500000
});
pending…
1mill items in array
// async test
window.testWorker.onmessage = function(e) {
  (new StringView(e.data)).toString();
  deferred.resolve();
};
window.testWorker.postMessage({
  method: 'ab',
  len: 1000000
});
pending…

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