JavaScript Program to Find Square Root of a Number

Use Math.sqrt(number) in JavaScript to find the square root of a number, for example, Math.sqrt(16) returns 4.

Examples

Input16

Output4

Input25

Output5

Input0

Output0

How to Think About It

To find the square root of a number, think about what number multiplied by itself gives the original number. We use the built-in Math.sqrt() function in JavaScript which does this calculation for us easily.

Algorithm

1

Get the input number from the user or code.

2

Use the built-in function to calculate the square root.

3

Return or print the result.

Code

javascript

const number = 16;
const squareRoot = Math.sqrt(number);
console.log('Square root of', number, 'is', squareRoot);

Output

Square root of 16 is 4

Dry Run

Let's trace the example where number = 16 through the code

1

Assign number

number = 16

2

Calculate square root

squareRoot = Math.sqrt(16) = 4

3

Print result

Output: 'Square root of 16 is 4'

Step	Variable	Value
1	number	16
2	squareRoot	4
3	output	'Square root of 16 is 4'

Why This Works

Step 1: Using Math.sqrt()

The Math.sqrt() function is built into JavaScript and returns the square root of the given number.

Step 2: Input and output

You provide a number as input, and it returns the positive square root as output.

Step 3: Printing the result

We use console.log() to show the result on the screen.

Alternative Approaches

Exponentiation operator

javascript

const number = 16;
const squareRoot = number ** 0.5;
console.log('Square root of', number, 'is', squareRoot);

This uses the power operator to find the square root by raising the number to 0.5 power; it's simple but less explicit than Math.sqrt().

Custom function using binary search

javascript

function sqrt(num) {
  if (num < 0) return NaN;
  let start = 0, end = num, mid;
  while (end - start > 0.00001) {
    mid = (start + end) / 2;
    if (mid * mid > num) end = mid;
    else start = mid;
  }
  return start;
}
console.log('Square root of 16 is', sqrt(16));

This method approximates the square root using binary search; useful if you want to avoid built-in functions but is more complex and slower.

Complexity: O(1) time, O(1) space

Time Complexity

Using Math.sqrt() is a constant time operation because it directly computes the result without loops.

Space Complexity

The operation uses constant space as it only stores a few variables.

Which Approach is Fastest?

Math.sqrt() is fastest and most efficient; exponentiation is also fast but less clear; custom methods like binary search are slower and more complex.

Approach	Time	Space	Best For
Math.sqrt()	O(1)	O(1)	Simple and fast square root calculation
Exponentiation operator	O(1)	O(1)	Quick alternative but less explicit
Binary search method	O(log n)	O(1)	Learning or custom approximation without built-ins