You are given a positive number n. Return the smallest number x greater than or equal to n, such that the binary representation of x contains only set bits

smallestNumber.js

/**
 * @param {number} n
 * @return {number}
 */
var smallestNumber = function(n) {
    // Start with 1 and keep shifting left and OR-ing to build numbers like 1, 3, 7, 15, 31, etc.
    let x = 1;

    // Keep generating numbers with all bits set until we find one >= n
    while (x < n) {
        // Shift left by 1 (multiply by 2) and add 1 to set the next bit
        x = (x << 1) | 1;
    }

    return x;
};