Search Element in an Javascript Hash Table

JavaScript hash tables use a get method to search for elements by their key. The method calculates the hash code and searches through the chain at that index to find the matching key-value pair.

The get() Method Implementation

The search operation involves computing the hash code for the given key and then iterating through the chain at that bucket to find the exact match:

get(key) {
    let hashCode = hash(key);
    for(let i = 0; i < this.container[hashCode].length; i ++) {
        // Find the element in the chain
        if(this.container[hashCode][i].key === key) {
            return this.container[hashCode][i];
        }
    }
    return undefined;
}

Complete Example

Here's how to test the search functionality with a complete hash table implementation:

// Simple hash function
function hash(key) {
    return key % 10;
}

// Hash table class with get method
class HashTable {
    constructor() {
        this.container = {};
        for(let i = 0; i < 10; i++) {
            this.container[i] = [];
        }
    }
    
    put(key, value) {
        let hashCode = hash(key);
        this.container[hashCode].push({key: key, value: value});
    }
    
    get(key) {
        let hashCode = hash(key);
        for(let i = 0; i < this.container[hashCode].length; i ++) {
            if(this.container[hashCode][i].key === key) {
                return this.container[hashCode][i];
            }
        }
        return undefined;
    }
}

// Testing the search functionality
let ht = new HashTable();

ht.put(10, 94);
ht.put(20, 72);
ht.put(30, 1);
ht.put(21, 6);
ht.put(15, 21);
ht.put(32, 34);

console.log(ht.get(20));
console.log(ht.get(21));
console.log(ht.get(55));
console.log(ht.get(32));

{ key: 20, value: 72 }
{ key: 21, value: 6 }
undefined
{ key: 32, value: 34 }

How It Works

The search process follows these steps:

1. Hash Calculation: Calculate the hash code using hash(key)
2. Bucket Access: Access the chain at this.container[hashCode]
3. Linear Search: Iterate through the chain to find matching key
4. Return Result: Return the key-value pair if found, otherwise undefined

Time Complexity

Conclusion

The hash table search operation provides efficient key-based lookups by combining hash computation with chain traversal. It returns the complete key-value pair object or undefined if the key doesn't exist.