JavaScript - Next power of two of a given number

JavaScript Bit Manipulation: Exercise-4 with Solution

Next Power of Two

Write a JavaScript program to find the next power of two of a given number.

A power of two is a number of the form 2n where n is an integer, that is, the result of exponentiation with number two as the base and integer n as the exponent.
The first ten powers of 2 for non-negative values of n are: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, ...

Test Data:
(1) -> 1
(4) -> 4
(9) -> 16
("15") -> "It must be number!"

Sample Solution:

JavaScript Code:

// Define a function to find the next power of two greater than the given number
const next_Power_Of_Two = (num) => {
      // Check if the input is not a number
      if (typeof num != "number") {
          return 'It must be number!' // Return an error message
      }

  // Check if the number is already a power of two
  if (num > 0 && (num & (num - 1)) === 0) 
    return num // Return the number itself if it is a power of two
  
  let result = 1 // Initialize the result as 1, which is the smallest power of two

  // Loop until the number becomes 0
  while (num > 0) 
  {
    result = result << 1 // Multiply the result by 2 by left shifting the bits
    num = num >> 1 // Divide the number by 2 by right shifting the bits
  }
  return result // Return the next power of two
}
console.log(next_Power_Of_Two(1)) // Test the function with the number 1
console.log(next_Power_Of_Two(4)) // Test the function with the number 4
console.log(next_Power_Of_Two(9)) // Test the function with the number 9
console.log(next_Power_Of_Two("15")) // Test the function with the string "15"

Output:

1
4
16
It must be number!

Flowchart:

Live Demo:

See the Pen javascript-bit-manipulation-exercise-4 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 finds the next power of two greater than or equal to a given number using bit manipulation.
• Write a JavaScript function that iteratively doubles a value until it is greater than or equal to the input number.
• Write a JavaScript function that validates the input and returns an error if it is not a number.
• Write a JavaScript function that uses logarithms and Math.ceil to compute the next power of two.

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