javascript - What is the best way to determine if a given number is a power of two? -

i need return true if n power of 2 , false otherwise. should go like:

function poweroftwo(n){   //code here } 

this way :

function ispoweroftwo(n){   var x = math.pow(2, math.round(math.log(n) / math.log(2)));   return x; } 

are there more effective ways ?

you can use ecmascript5 math.log:

function poweroftwo(x) {     return (math.log(x)/math.log(2)) % 1 === 0; } 

remember, in math, logarithm arbitrary base, can divide log₁₀ of operand (x in case) log₁₀ of base. , see if number regular integer (and not floating point), check if remainder 0 using modulus % operator.

in ecmascript6 can this:

function poweroftwo(x) {     return math.log2(x) % 1 === 0; } 

see mdn docs math.log2.