208.实现-trie-前缀树.js

/*
 * @lc app=leetcode.cn id=208 lang=javascript
 *
 * [208] 实现 Trie (前缀树)
 */
/**
 * Initialize your data structure here.
 */
var Trie = function() {
  this.map = new Map()
}

/**
 * Inserts a word into the trie.
 * @param {string} word
 * @return {void}
 */
Trie.prototype.insert = function(word) {
  this.map.set(word, true)
}

/**
 * Returns if the word is in the trie.
 * @param {string} word
 * @return {boolean}
 */
Trie.prototype.search = function(word) {
  return this.map.has(word)
}

/**
 * Returns if there is any word in the trie that starts with the given prefix.
 * @param {string} prefix
 * @return {boolean}
 */
Trie.prototype.startsWith = function(prefix) {
  for (const key of this.map.keys()) {
    if (prefix === key.substr(0, prefix.length)) return true
  }
  return false
}