比较十六进制字符串

Question

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

Answer 1

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