# JavaScript - Binary logarithm using bitwise operators

## JavaScript Bit Manipulation: Exercise-8 with Solution

Write a JavaScript program to calculate the binary logarithm (log_{2}n) using bitwise operators.

From handwiki.org -

Binary logarithm:

In mathematics, the binary logarithm (log_{2}n) is the power to which the number 2 must be raised to obtain the value n. That is, for any real number x,

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 log_{2}, 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: **

**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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## 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]

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