chore(JavaScript): add trie implementations algorithm (MakeContributi…

…ons#863)

Co-authored-by: Ming Tsai <[email protected]>

algorithms/JavaScript/README.md

@@ -49,3 +49,7 @@
 
 - [Max Heap](src/heaps/max-heap.js)
 - [Min Heap](src/heaps/min-heap.js)
+
+## Trie
+
+- [Trie Implementation](src/trie/trie-implementation.js)

algorithms/JavaScript/src/trie/trie-implementation.js

@@ -0,0 +1,79 @@
+/*
+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.
+
+Insertion:
+Average Case: O(N)
+Worst Case: O(N)
+Best Case: O(N)
+
+Deletion:
+Average Case: O(N)
+Worst Case: O(N)
+Best Case: O(N)
+
+Searching:
+Average Case: O(N)
+Worst Case: O(N)
+Best Case: O(1)
+
+Space complexity: O(alphabet_size * average key length * N)
+*/
+
+/*
+Create a node that will have two properties —
+one is the hash map for storing children.
+the other one is for keeping track of the end of the word.
+*/
+
+class Node {
+  constructor() {
+    this.children = {};
+    this.isEndWord = false;
+  }
+}
+
+class Trie {
+  constructor() {
+    this.root = new Node();
+  }
+  insert(word) {
+    let node = this.root;
+    for (const char of word) {
+      if (!node.children[char]) {
+        node.children[char] = new Node();
+      }
+      node = node.children[char];
+    }
+    node.isEndWord = true;
+  }
+  search(word) {
+    let node = this.root;
+    for (const char of word) {
+      if (!node.children[char]) {
+        return false;
+      }
+      node = node.children[char];
+    }
+    return node.isEndWord ? true : false;
+  }
+  startsWith(prefix) {
+    let node = this.root;
+    for (const char of prefix) {
+      if (!node.children[char]) {
+        return false;
+      }
+      node = node.children[char];
+    }
+    return true;
+  }
+}
+
+const trie = new Trie();
+trie.insert('datastructures');
+trie.insert('datablock');
+console.log(trie.search('dsa')); // false
+console.log(trie.search('datablock')); // true
+console.log(trie.startsWith('data')); // true