Like the title

During the interaction with the hardware device, a hexadecimal number is received from the hardware, with the low digit in front and the high digit in the back. How to elegantly parse it into the correct decimal data?

//举例 16进制的一个数据
var num=0x12345678
//因为低位在前，高位在后，正确解析后是
num=0x78563412
//转换成10进制是
num=2018915346

Current processing method:
Cut num according to length, then change the order before and after through a for loop, and finally convert parseInt to decimal, which achieves the goal. I feel that this method is definitely unreasonable. I am looking for a more standard approach.