code: function arrayCopy(src, srcOffset, dest, destOffset, count) {
      if (count == 0) {
          return;
      } 
      if (!src) {
          throw "Undef src";
      } else if (!dest) {
          throw "Undef dest";
      }
  
      if (srcOffset == 0 && count == src.length) {
          arrayCopy_fast(src, dest, destOffset);
      } else if (hasSubarray) {
          arrayCopy_fast(src.subarray(srcOffset, srcOffset + count), dest, destOffset); 
      } else if (src.BYTES_PER_ELEMENT == 1 && count > 100) {
          arrayCopy_fast(new Uint8Array(src.buffer, src.byteOffset + srcOffset, count), dest, destOffset);
      } else { 
          arrayCopy_slow(src, srcOffset, dest, destOffset, count);
      }
  
  }
docs: /* (typeof testArray.slice === 'function'); Chrome slice performance is so dire that we're currently not using it...