Let\'s say I have a hex data stream, which I want to divide into 3-bytes blocks which I need to read as an integer.
For example: given a hex string 01be638119704d4
If you are using node.js v0.12+ or io.js, there is buffer.readUIntBE() which allows a variable number of bytes:
var decimal = buffer.readUIntBE(0, 3);
(Note that it's readUIntBE for Big Endian and readUIntLE for Little Endian).
Otherwise if you're on an older version of node, you will have to do it manually (check bounds first of course):
var decimal = (buffer[0] << 16) + (buffer[1] << 8) + buffer[2];