Reading select bytes in numeric values

Question

We are receiving a single 32 bit integer value from a server

{
"value": -1072678909
}

In reality they have packed four separate 1 byte values into this one number so we need to read each byte separately to get its value. in this case...

note: reading from right to left

• The first byte is 00000011 (e.g. value of 3)
• The second byte is 00111000 (e.g. value of 56)
• The third byte is 00010000 (e.g. value of 16)
• The fourth byte is 11000000 (e.g. value of 192)

How can we accomplish this in JavaScript?

Answer 1

Pretty easy using bitshifting and masks:

var byte1 = val & 0xff;
var byte2 = (val>>8) & 0xff;
var byte3 = (val>>16) & 0xff;
var byte4 = (val>>24) & 0xff;