A trie (pronounced as “try”) or prefix tree is a tree data structure used to efficiently store and retrieve keys in a dataset of strings. There are various applications of this data structure, such as autocomplete and spellchecker.

Implement the Trie class:

• Trie() Initializes the trie object.
• void insert(String word) Inserts the string word into the trie.
• boolean search(String word) Returns true if the string word is in the trie (i.e., was inserted before), and false otherwise.
• boolean startsWith(String prefix) Returns true if there is a previously inserted string word that has the prefix prefix, and false otherwise.

Example

Input
["Trie", "insert", "search", "search", "startsWith", "insert", "search"]
[[], ["apple"], ["apple"], ["app"], ["app"], ["app"], ["app"]]
Output
[null, null, true, false, true, null, true]

Explanation
Trie trie = new Trie();
trie.insert("apple");
trie.search("apple");   // return True
trie.search("app");     // return False
trie.startsWith("app"); // return True
trie.insert("app");
trie.search("app");     // return True

Solution

Helpful solution found here.

//Class to represent a node in the trie
class TrieNode {
    constructor() {
    this.children = {}
    this.endWord = false
    }
}

var Trie = function() {
    //Initializes the trie object
    this.root = new TrieNode()
};

Trie.prototype.insert = function(word) {
    //Inserts the string word into the trie
    let curr = this.root
    for(let cha of word) {
        //if the character is not in the trie, add it
        if(!curr.children[cha]) {
            //create a new node for the character
             curr.children[cha] = new TrieNode()
        } 
        curr = curr.children[cha]
    }
    //mark the end of the word
    curr.endWord = true
};

//Returns true if the string word is in the trie (i.e., was inserted before), and false otherwise.
Trie.prototype.search = function(word) {
    let curr = this.root
    for(let cha of word) {
        if(!curr.children[cha]) {
            return false
        }
        curr = curr.children[cha]
    }
    //if the word is a prefix of another word, return false
    return (curr.endWord == true) ? true : false
};

//Returns true if there is a previously inserted string word that has the prefix prefix, and false otherwise.
Trie.prototype.startsWith = function(prefix) {
    let curr = this.root
    for(let cha of prefix) {
        if(!curr.children[cha]) {
            return false
        }
        //if the character is in the trie, move to the next character
        curr = curr.children[cha]
    }
    return true
};