Simplify deletion method of TrieNode.

src/data-structures/trie/TrieNode.js

@@ -42,20 +42,16 @@ export default class TrieNode {
    * @return {TrieNode}
    */
   removeChild(character) {
-    function isSafeToDelete(node) {
-      return (
-        node
-        && !node.isCompleteWord
-        && node.children.getKeys().length === 0
-      );
-    }
-
     const childNode = this.getChild(character);
 
-    // delete childNode only if:
-    // - childNode has NO children
-    // - childNode.isCompleteWord === false
-    if (isSafeToDelete(childNode)) {
+    // Delete childNode only if:
+    // - childNode has NO children,
+    // - childNode.isCompleteWord === false.
+    if (
+      childNode
+      && !childNode.isCompleteWord
+      && !childNode.hasChildren()
+    ) {
       this.children.delete(character);
     }
 
@@ -70,6 +66,14 @@ export default class TrieNode {
     return this.children.has(character);
   }
 
+  /**
+   * Check whether current TrieNode has children or not.
+   * @return {boolean}
+   */
+  hasChildren() {
+    return this.children.getKeys().length !== 0;
+  }
+
   /**
    * @return {string[]}
    */

src/data-structures/trie/__test__/TrieNode.test.js

@@ -30,6 +30,16 @@ describe('TrieNode', () => {
     expect(trieNode.getChild('b')).toBeUndefined();
   });
 
+  it('should check if node has children', () => {
+    const trieNode = new TrieNode('c');
+
+    expect(trieNode.hasChildren()).toBe(false);
+
+    trieNode.addChild('a');
+
+    expect(trieNode.hasChildren()).toBe(true);
+  });
+
   it('should check if node has specific child', () => {
     const trieNode = new TrieNode('c');