You are given a binary array nums (0-indexed). We define xi as the number whose binary representation is the subarray nums[0..i] (from most-significant-bit to least-significant-bit). For example, if nums = [1,0,1], then x0 = 1, x1 = 2, and x2 = 5.

prefixesDivBy5.js

/**
 * @param {number[]} nums
 * @return {boolean[]}
 */
var prefixesDivBy5 = function(nums) {
    // Result array to store true/false for each prefix
    let answer = [];

    // We'll keep track of the current number modulo 5
    // This avoids dealing with huge binary numbers directly
    let currentMod = 0;

    // Iterate through each bit in nums
    for (let i = 0; i < nums.length; i++) {
        // Shift left (multiply by 2) and add the new bit
        // Example: if currentMod = 2 (binary '10') and nums[i] = 1,
        // new number = '101' -> decimal 5
        currentMod = (currentMod * 2 + nums[i]) % 5;

        // If currentMod is 0, then the number is divisible by 5
        answer.push(currentMod === 0);
    }

    return answer;
};