https://leetcode.com/problems/add-and-search-word-data-structure-design/

addAndSearchWord.js

/**
 * Initialize your data structure here.
 */
var WordDictionary = function() {
    this.storage = new Array(26).fill(null);
};

/**
 * Adds a word into the data structure. 
 * @param {string} word
 * @return {void}
 */
WordDictionary.prototype.addWord = function(word) {
    this._add(word, 0, this.storage);
};

WordDictionary.prototype._add = function(word, i, root) {
    if(i >= word.length) return root.isTerminal = true;
    const c = word.charCodeAt(i) - 97;
    if(!root[c]) root[c] = new Array(26).fill(null);
    this._add(word, i+1, root[c]);
};

/**
 * Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. 
 * @param {string} word
 * @return {boolean}
 */
WordDictionary.prototype.search = function(word) {
    return this._search(word, 0, this.storage);
};

WordDictionary.prototype._search = function(word, i, root){
    if(i === word.length) return !!root.isTerminal;
    
    if(word[i] === '.'){
        // try all nodes in this root
        for(let j=0; j<root.length; j++){
            if(!root[j]) continue;
            if(this._search(word, i+1, root[j])) return true;
        }
        return false;
    }
    
    const c = word.charCodeAt(i) - 97;
    if(!root[c]) return false; 
    return this._search(word, i+1, root[c]);
};