208. Implement Trie (Prefix Tree) 实现前缀树

 Implement a trie with insert, search, and startsWith methods.

Note:
You may assume that all inputs are consist of lowercase letters a-z. 

var Trie = function() {
    this.nodes = {};
};
Trie.prototype.insert = function(word) {
    let node = this.nodes, cur;
    for (let i = 0; i < word.length; i++) {
        cur = word[i];
        if (!node[cur]) {
            node[cur] = {};
        }
        node = node[cur];
    }
    node.isWord = true;
};
Trie.prototype.search = function(word) {
    let node = this.nodes, cur;
    for (let i = 0; i < word.length; i++) {
        cur = word[i];
        if (!node[cur]) {
            return false;
        }
        node = node[cur];
    }
    return node.isWord == true;
};
Trie.prototype.startsWith = function(prefix) {
    let node = this.nodes, cur;
    for (let i = 0; i < prefix.length; i++) {
        cur = prefix[i];
        if (!node[cur]) {
            return false;
        }
        node = node[cur];
    }
    return true;
};

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