Modbus: convert hex value to dword in nodejs

Question

Specification given in the manual of meter which uses modbus as communication protocol:

“dword” refers to 32-bit unsigned integer using two data addresses and 4 bytes
of memory with high word at the front and low word at the end, it varies from 0
to 4294967295. rx = high word *65536+low word

i have this hexValue : 00003ef5.

where highword = 0000 and lowword = 3ef5

so rx would be 3ef5 and this converted to decimal gives 16,117.

For now i have used this:

var rx = hexValue.substr(0,4)*65536 + hexValue.substr(4,8);
console.log(parseInt(rx,16));

Is there a way to convert my hex value directly to dword using nodejs buffer library or any other method better than this?