LeetCode - 30 - Substring with Concatenation of All Words

 /**

 * @param {string} s
 * @param {string[]} words
 * @return {number[]}
 */
var findSubstring = function(s, words) {
    var hash = {};
    var wordLength = words[0].length;
    var wordsTotal = wordLength * words.length;
    for (const word of words) {
        if (hash[word]) {
            hash[word]++;
        } else {
            hash[word] = 1;
        }
    }

    var slidingWindow = [];
    var sol = [];
    for(var i = 0; i < s.length ; i++) {
        if (slidingWindow.length < wordsTotal - 1) {
            slidingWindow.push(s[i]);
        } else {
            slidingWindow.push(s[i]);
            if (isPermutationOfWords(slidingWindow.join(''), Object.assign({}, hash), wordLength)) {
                sol.push(i - wordsTotal + 1);
            }
            slidingWindow.shift();
        }
    }
    return sol;
};

function isPermutationOfWords(s, words, wordLength) {
    var str = "";
    for(var i = 0; i < s.length; i++) {
        str += s[i];
        if (str.length == wordLength) {
            if (words[str]) {
                words[str]--;
                str = "";
            } else {
                return false;
            }
        }
    }
    return true;
}