Node.js: How do you implement a custom memory-efficient data structure?

1// Trie for string storage
2class Trie {
3    constructor() {
4        this.root = {};
5    }
6
7    insert(word) {
8        let node = this.root;
9        for (const char of word) {
10            if (!node[char]) node[char] = {};
11            node = node[char];
12        }
13        node.isEnd = true;
14    }
15
16    search(word) {
17        let node = this.root;
18        for (const char of word) {
19            if (!node[char]) return false;
20            node = node[char];
21        }
22        return node.isEnd === true;
23    }
24
25    startsWith(prefix) {
26        let node = this.root;
27        for (const char of prefix) {
28            if (!node[char]) return false;
29            node = node[char];
30        }
31        return true;
32    }
33}
34
35// Compact array for small integers
36class CompactArray {
37    constructor(maxValue) {
38        this.bitsPerElement = Math.ceil(Math.log2(maxValue + 1));
39        this.bytesPerElement = Math.ceil(this.bitsPerElement / 8);
40    }
41
42    encode(arr) {
43        const buffer = Buffer.alloc(arr.length * this.bytesPerElement);
44        arr.forEach((val, i) => {
45            buffer.writeUIntLE(val, i * this.bytesPerElement, this.bytesPerElement);
46        });
47        return buffer;
48    }
49
50    decode(buffer) {
51        const arr = [];
52        for (let i = 0; i < buffer.length; i += this.bytesPerElement) {
53            arr.push(buffer.readUIntLE(i, this.bytesPerElement));
54        }
55        return arr;
56    }
57}
58
59// Usage
60const trie = new Trie();
61trie.insert("hello");
62trie.insert("world");
63console.log(trie.search("hello")); // true
64console.log(trie.startsWith("wor")); // true