CODEWITHSUNDEEP
javascripthex
kzaiwo
kzaiwo

Reputation: 1748

Compare hex string

I am trying to decode a series of hex strings and check some of their nibbles.

In the example below, I am checking string (hexString) and checking it if the last 5 bits are set to true (0x1f). However, it is returning false. How can I check a hex string's bits?

const hexString = 'f0'

const areFiveLowestBitsSet = (hexString && 0x1f) === 0x1f
console.log(areFiveLowestBitsSet)  // prints true

Upvotes: 1

Views: 2219

Answers (1)

T.J. Crowder
T.J. Crowder

Reputation: 1074258

There are two problems:

  1. You're not parsing the string to get a number

  2. You're using &&, which is a logical operator, not the bitwise operator &

Parse the number as hex (parseInt(hexString, 16)) and use the bitwise operator:

let hexString = 'f0'

let areFiveLowestBitsSet = (parseInt(hexString, 16) & 0x1f) === 0x1f;
// −−−−−−−−−−−−−−−−−−−−−−−−−^^^^^^^^^^^^^^^^^^^^^^^−^
console.log(areFiveLowestBitsSet); // false

hexString = '3f';
areFiveLowestBitsSet = (parseInt(hexString, 16) & 0x1f) === 0x1f;
// −−−−−−−−−−−−−−−−−−−−−^^^^^^^^^^^^^^^^^^^^^^^−^
console.log(areFiveLowestBitsSet); // true

Upvotes: 1

Related Questions