JavaScript - Check if k^th bit is set or not for a number

JavaScript Bit Manipulation: Exercise-11 with Solution

Check kth Bit

Write a JavaScript program to check whether the k^th bit is set or not in a given number. Return true if the k^th bit is set otherwise false.

In a binary representation the presence of a non-zero value indicates that the k'th bit is set.

Test Data:
(33, 1) -> true
Explanation:
Binary format of 33 is -> 100001
K =1 -> kth bit is 1 [Non-zero value indicates that the k'th bit is set.]
(33, 2) -> false
Explanation:
Binary format of 33 is -> 100001
K =2 -> kth bit is 0 [Zero value indicates that the k'th bit is not set.]

Sample Solution:

JavaScript Code:

// Define a function to check if the kth bit of a number is set or not
const turn_On_Kth_Bit = (n, k) => {
  // Check if the input is not a number
  if (typeof n != "number") {
    return 'It must be number!'; // Return an error message
  }
  // Return true if the kth bit is set, false otherwise
  return (n & (1 << (k - 1))) != 0;
}

// Initialize variables n and k with values
let n = 33;
let k = 1;

// Display the binary representation of n
console.log(n + " in binary is " + n.toString(2));
console.log("k = " + k);

// Call the turn_On_Kth_Bit function to check if the kth bit is set
let result_n = turn_On_Kth_Bit(n, k);
console.log("Check kth bit is set or not in the said number! " + result_n);

// Update variable k with a new value
k = 2;

// Display the binary representation of n
console.log(n + " in binary is " + n.toString(2));
console.log("k = " + k);

// Call the turn_On_Kth_Bit function to check if the kth bit is set
result_n = turn_On_Kth_Bit(n, k);
console.log("Check kth bit is set or not in the said number! " + result_n);

Output:

33 in binary is 100001
k = 1
Check kth bit is set or not in the said number! true
33 in binary is 100001
k = 2
Check kth bit is set or not in the said number! false

Flowchart:

Live Demo:

See the Pen javascript-bit-manipulation-exercise-11 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 checks if the kth bit in a given number is set by using bitwise AND with a shifted mask.
• Write a JavaScript function that returns true if the kth bit is 1, otherwise false, and validates the index.
• Write a JavaScript function that converts the number to a binary string and checks the kth character for "1".
• Write a JavaScript function that handles negative numbers by taking the absolute value before bit-checking.

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