JavaScript - Swap two bits at given position in an integer

JavaScript Bit Manipulation: Exercise-7 with Solution

Swap Bits

Write a JavaScript program to swap two bits (from the right side, the rightmost position is 0) in the binary representation of an integer at the given position.

Test Data:
(245) -> 249

Explanation:
245 -> 11110101
Swap the 1st and 4th bits from the side of the said binary number.
11100111 -> 231
(137) -> 73
Explanation:
137 -> 10001001
Swap the 6th and 7th bits from the side of the said binary number.
01001001 -> 73

Sample Solution:

JavaScript Code:

// Define a function to swap bits at given positions in a number
const swap_bits = (n, pos1, pos2) => {
   // Check if the input is not a number
   if (typeof n!= "number") {
          return 'It must be number!' // Return an error message
      }
   // Check if the XOR of the bits at the given positions is 1
   if ((((n & (1 << pos1)) >> pos1) ^ ((n & (1 << pos2)) >> pos2)) == 1)
        {
            n ^= (1 << pos1); // Swap the bits at position pos1
            n ^= (1 << pos2); // Swap the bits at position pos2
        }
   return n; // Return the number after swapping the bits
}
console.log(swap_bits(245,1,4)) // Test the function with the number 245, swapping bits at positions 1 and 4
console.log(swap_bits(137,6,7)) // Test the function with the number 137, swapping bits at positions 6 and 7
console.log(swap_bits("16")) // Test the function with the string "16"

Output:

231
73
It must be number!

Flowchart:

Live Demo:

See the Pen javascript-bit-manipulation-exercise-7 by w3resource (@w3resource) on CodePen.

* To run the code mouse over on Result panel and click on 'RERUN' button.*

For more Practice: Solve these Related Problems:

• Write a JavaScript function that swaps the bits at two specified positions in the binary representation of a number.
• Write a JavaScript function that validates the bit positions and returns an error if they are out of range.
• Write a JavaScript function that uses bit masks and bitwise OR/AND to swap the kth and jth bits of a number.
• Write a JavaScript function that prints the binary representation before and after swapping specified bits.

Go to:

• JavaScript Bit Manipulation Exercises Home ↩
• JavaScript Exercises Home ↩

PREV : Power of Four Check.
NEXT : Binary Logarithm (log2n).

Improve this sample solution and post your code through Disqus.