JavaScript - Check a number is a power of 4 or not
JavaScript Bit Manipulation: Exercise-6 with Solution
Write a JavaScript program to check a given positive number is a power of four or not using bit manipulation.
The expression n & (n-1) will unset the rightmost set bit of a number. If the number is a power of 2, it has only a 1-bit set, and n & (n-1) will unset the only set bit. So, we can say that n & (n-1) returns 0 if n is a power of 2; otherwise, it's not a power of 2.
The mask 0xAAAAAAAA will allow us to determine where the set bit is located. In all of its odd positions, the mask 0xAAAAAAAA has a value of 1. The set bit in n will be even if the expression (n & 0xAAAAAAAA) is true.
(0xAAAAAAAA)16 = (10101010101010101010101010101010)2.
Test Data:
(256) -> true
(4) -> true
(2) -> false
("16") -> "It must be number!"
Sample Solution:
JavaScript Code:
const Power_of_four = (n) => {
if (typeof n!= "number") {
return 'It must be number!'
}
return n != 0 && (n & (n - 1)) == 0 && (n & 0xAAAAAAAA) == 0;
}
console.log(Power_of_four(256))
console.log(Power_of_four(4))
console.log(Power_of_four(2))
console.log(Power_of_four("16"))
Sample Output:
true true false It must be number!
Flowchart:

Live Demo:
See the Pen javascript-bit-manipulation-exercise-6 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: Odd or even number using bit manipulation.
Next: Swap two bits at given position in an integer.
What is the difficulty level of this exercise?
Test your Programming skills with w3resource's quiz.
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]
- Weekly Trends
- Java Basic Programming Exercises
- SQL Subqueries
- Adventureworks Database Exercises
- C# Sharp Basic Exercises
- SQL COUNT() with distinct
- JavaScript String Exercises
- JavaScript HTML Form Validation
- Java Collection Exercises
- SQL COUNT() function
- SQL Inner Join
- JavaScript functions Exercises
- Python Tutorial
- Python Array Exercises
- SQL Cross Join
- C# Sharp Array Exercises