w3resource

JavaScript - Binary logarithm using bitwise operators

JavaScript Bit Manipulation: Exercise-8 with Solution

Write a JavaScript program to calculate the binary logarithm (log2n) using bitwise operators.

From handwiki.org -
Binary logarithm:
In mathematics, the binary logarithm (log2n) is the power to which the number 2 must be raised to obtain the value n. That is, for any real number x,
Binary Logarithm
For example, the binary logarithm of 1 is 0, the binary logarithm of 2 is 1, the binary logarithm of 4 is 2, and the binary logarithm of 32 is 5.
The binary logarithm is the logarithm to the base 2 and is the inverse function of the power of two function. As well as log2, an alternative notation for the binary logarithm is lb (the notation preferred by ISO 31-11 and ISO 80000-2).

Test Data:
(1) -> 0
(2) -> 1
(4) -> 2
(32) -> 5

Sample Solution:

JavaScript Code:

const log_Two = (n) => {
 if (typeof n!= "number") {
     return 'It must be number!'
     }
  let result = 0
  while (n >> 1) {
    n >>= 1
    result++
  }
  return result
}
console.log(log_Two(1))
console.log(log_Two(2))
console.log(log_Two(4))
console.log(log_Two(32))

Sample Output:

0
1
2
5

Flowchart:

Flowchart: JavaScript - Binary logarithm using bitwise operators.

Live Demo:

See the Pen javascript-bit-manipulation-exercise-8 by w3resource (@w3resource) on CodePen.


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

Improve this sample solution and post your code through Disqus

Previous: Swap two bits at given position in an integer.
Next: Turn off the kth bit of a given number.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



Share this Tutorial / Exercise on : Facebook and Twitter

JavaScript: Tips of the Day

function and arguments

const person = {
  name: 'Lydia Hallie',
  hobbies: ['coding'],
};

function addHobby(hobby, hobbies = person.hobbies) {
  hobbies.push(hobby);
  return hobbies;
}

addHobby('running', []);
addHobby('dancing');
addHobby('baking', person.hobbies);

console.log(person.hobbies);

The addHobby function receives two arguments, hobby and hobbies with the default value of the hobbies array on the person object.
First, we invoke the addHobby function, and pass "running" as the value for hobby and an empty array as the value for hobbies. Since we pass an empty array as the value for y, "running" gets added to this empty array.
Then, we invoke the addHobby function, and pass "dancing" as the value for hobby. We didn't pass a value for hobbies, so it gets the default value, the hobbies property on the person object. We push the hobby dancing to the person.hobbies array.
Last, we invoke the addHobby function, and pass "bdaking" as the value for hobby, and the person.hobbies array as the value for hobbies. We push the hobby baking to the person.hobbies array.
After pushing dancing and baking, the value of person.hobbies is ["coding", "dancing", "baking"]

Ref: https://bit.ly/2Hcpkm6