feat: add js solution to lc problem: No.0208.Implement Trie (Prefix Tree) (doocs#398)

Author: zhaocchen

solution/0200-0299/0208.Implement Trie (Prefix Tree)/README.md

@@ -200,6 +200,69 @@ class Trie {
  */
 ```
 
+### **JavaScript**
+
+```js
+/**
+ * Initialize your data structure here.
+ */
+var Trie = function() {
+    this.children = {};
+};
+
+/**
+ * Inserts a word into the trie. 
+ * @param {string} word
+ * @return {void}
+ */
+Trie.prototype.insert = function(word) {
+    let node = this.children;
+    for (let char of word) {
+        if (!node[char]) {
+            node[char] = {};
+        }
+        node = node[char];
+    }
+    node.isEnd = true;
+};
+
+/**
+ * Returns if the word is in the trie. 
+ * @param {string} word
+ * @return {boolean}
+ */
+Trie.prototype.search = function(word) {
+    let node = this.searchPrefix(word);
+    return node != undefined && node.isEnd != undefined;
+};
+
+Trie.prototype.searchPrefix = function (prefix) {
+    let node = this.children;
+    for (let char of prefix) {
+        if (!node[char]) return false;
+        node = node[char];
+    }
+    return node;
+}
+
+/**
+ * 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) {
+    return this.searchPrefix(prefix);
+};
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * var obj = new Trie()
+ * obj.insert(word)
+ * var param_2 = obj.search(word)
+ * var param_3 = obj.startsWith(prefix)
+ */
+```
+
 ### **...**
 
 ```

solution/0200-0299/0208.Implement Trie (Prefix Tree)/README_EN.md

@@ -165,6 +165,69 @@ class Trie {
  */
 ```
 
+### **JavaScript**
+
+```js
+/**
+ * Initialize your data structure here.
+ */
+var Trie = function() {
+    this.children = {};
+};
+
+/**
+ * Inserts a word into the trie. 
+ * @param {string} word
+ * @return {void}
+ */
+Trie.prototype.insert = function(word) {
+    let node = this.children;
+    for (let char of word) {
+        if (!node[char]) {
+            node[char] = {};
+        }
+        node = node[char];
+    }
+    node.isEnd = true;
+};
+
+/**
+ * Returns if the word is in the trie. 
+ * @param {string} word
+ * @return {boolean}
+ */
+Trie.prototype.search = function(word) {
+    let node = this.searchPrefix(word);
+    return node != undefined && node.isEnd != undefined;
+};
+
+Trie.prototype.searchPrefix = function (prefix) {
+    let node = this.children;
+    for (let char of prefix) {
+        if (!node[char]) return false;
+        node = node[char];
+    }
+    return node;
+}
+
+/**
+ * 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) {
+    return this.searchPrefix(prefix);
+};
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * var obj = new Trie()
+ * obj.insert(word)
+ * var param_2 = obj.search(word)
+ * var param_3 = obj.startsWith(prefix)
+ */
+```
+
 ### **...**
 
 ```

solution/0200-0299/0208.Implement Trie (Prefix Tree)/Solution.js

@@ -0,0 +1,58 @@
+/**
+ * Initialize your data structure here.
+ */
+ var Trie = function() {
+    this.children = {};
+};
+
+/**
+ * Inserts a word into the trie. 
+ * @param {string} word
+ * @return {void}
+ */
+Trie.prototype.insert = function(word) {
+    let node = this.children;
+    for (let char of word) {
+        if (!node[char]) {
+            node[char] = {};
+        }
+        node = node[char];
+    }
+    node.isEnd = true;
+};
+
+/**
+ * Returns if the word is in the trie. 
+ * @param {string} word
+ * @return {boolean}
+ */
+Trie.prototype.search = function(word) {
+    let node = this.searchPrefix(word);
+    return node != undefined && node.isEnd != undefined;
+};
+
+Trie.prototype.searchPrefix = function (prefix) {
+    let node = this.children;
+    for (let char of prefix) {
+        if (!node[char]) return false;
+        node = node[char];
+    }
+    return node;
+}
+
+/**
+ * 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) {
+    return this.searchPrefix(prefix);
+};
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * var obj = new Trie()
+ * obj.insert(word)
+ * var param_2 = obj.search(word)
+ * var param_3 = obj.startsWith(prefix)
+ */