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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.*

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Previous: Swap two bits at given position in an integer.
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JavaScript: Tips of the Day

Returns the symmetric difference between two arrays, after applying the provided function to each array element of both

Example:

const tips_symmetricDifference = (x, y, fn) => {
  const sA = new Set(x.map(v => fn(v))),
    sB = new Set(y.map(v => fn(v)));
  return [...x.filter(x => !sB.has(fn(x))), ...y.filter(x => !sA.has(fn(x)))];
};

console.log(tips_symmetricDifference([3.5, 5.5], [5.5, 7.5], Math.floor));

Output:

[3.5, 7.5]