How do I use a typed array with offset in node?

I am writing a mat file parser using jBinary, which is built on top of jDataView. I have a working parser with lots of tests, but it runs very slowly for moderately sized data sets of around 10 MB. I profiled with look and found that a lot of time is spent in tagData. In the linked tagData code, ints/uints/single/doubles/whatever are read one by one from the file and pushed to an array. Obviously, this isn't super-efficient. I want to replace this code with a typed array view of the underlying bytes to remove all the reading and pushing.

I have started to migrate the code to use typed arrays as shown below. The new code preserves the old functionality for all types except 'miINT8'. The new functionality tries to view the buffer b starting at offset s and with length l, consistent with the docs. I have confirmed that the s being passed to the Int8Array constructor is non-zero, even going to far as to hard code it to 5. In all cases, the output of console.log(elems.byteOffset) is 0. In my tests, I can see that the Int8Array is indeed starting from the beginning of the buffer and not at offset s as I intend.

What am I doing wrong? How do I get the typed array to start at position s instead of position 0? I have tested this on node.js version 10.25 as well as 12.0 with the same results in each case. Any guidance appreciated as I'm totally baffled by this one!

tagData: jBinary.Template({
      baseType: ['array', 'type'],
      read: function (ctx) {
        var view = this.binary.view
        var b = view.buffer
        var s = view.tell()
        var l = ctx.tag.numBytes
        var e = s + l
        var elems
        switch (ctx.tag.type) {
          case 'miINT8':  
            elems = new Int8Array(b,s,l); view.skip(l); console.log(elems.byteOffset); break;

          default:
            elems = []
            while (view.tell() < e && view.tell() < view.byteLength) {
              elems.push(this.binary.read(ctx.tag.type))
            }
        }


        return elems
      }
  }),