Circular Permutation in Binary Representation.js

var circularPermutation = function(n, start) {
    const grayCodes = [];
    
    let startIdx = -1;
    
    for (let i = 0; i <= 2**n - 1; i++) {
        grayCodes[i] = i ^ (i >> 1);
        
        if (grayCodes[i] == start) startIdx = i;
    }
    
    const res = [];
    
    for (let i = 0; i <= 2**n - 1; i++) {
        res[i] = grayCodes[startIdx];
        
        startIdx++;
        
        if (startIdx == grayCodes.length) startIdx = 0;
    }
   
    return res;
};