"index out of range" with dynamic array size

I add new elements to the data i read in but on save i get the “index out of range” error when i call writeAll(data).

“array(baseType, @length) - array of given type and length, reads/writes to the end of binary if length is not given.” I did not specify length. So i assumed it would be able to still save if i add more entries to the array than there was before - but it only works if i remove or keep the number the same.

    file: {
        recordNum: "int32",
        fieldNum: "int32",
        recordSize: "int32",
        data: ["array", dataFld"]
    }

RangeError: Index out of range
    at checkInt (buffer.js:1187:11)
    at Buffer.writeInt32LE (buffer.js:1375:5)

I store the jbinary object:

            loadedJBinary = binary;
            resolve({ data: loadedJBinary.readAll() });

And use it again to write: loadedJBinary.writeAll(data);

Because i saw no way to use a existing js object to create a new jBinary object to save. But this does not work with the increasing array size.

Nether did i find any way to update the size of arrays before writeall.

Can just hope this project isn’t dead, it’s the only one in existence that i could find that allows use of a C++ like struct approach.

[Ketec]

Found a way around the issue. I forgot the file had a header that specified each block size and count so i could calculate new buffer size from it.

[Ketec]

I do not know the byte size of a js object (because the null terminated strings are shorter and do not include the 00 bytes - so the string may only be 2 bytes in object but it should be 64 bytes in final data).

I found binary.view.byteLength to get the current length from another issue - but i still lack away to get the value to increase it by. Is there a way to calculate it / get the byte size of a type ( ex. dataFld.byteLength so i can just add x number of that value)?