js hashtable
// A hash table is data structure that uses a an array and a hashing function to store and lookup data stored in key value pairs.
// It also implements a collision strategy to handle multiple hashes that may produce the same index.
// In my example I will use seperate chaining to handle hash collisions, which means we can store multiple key value pairs in the same index using a map or an array, or a linked list. I will be using maps.
class HashTable {
constructor(size = 0) {
this.size = size;
this.hashMap = new Array(size)
for(let i = 0; i < this.size; i++) {
this.hashMap[i] = new Map();
}
}
// Hash our key and return the outputed idx % our hashtable size
hash(key) {
let hash = 0;
for (let i = 0; i < key.length; i++) {
hash += key.charCodeAt(i);
}
return hash % this.size;
}
// Insert key value pair at hashed idx
insert(key, value) {
const idx = this.hash(key);
this.hashMap[idx].set(key, value);
return;
}
// Remove an item at hashed idx
remove(key) {
let idx = this.hash(key);
let removedItem = this.hashMap[idx].get(key);
if(removedItem) {
// Remove the item and return it
this.hashMap[idx].delete(key);
return console.log('REMOVED: ' + removedItem);
}
return null;
}
// Retrieve a value at hashed idx
retrieve(key) {
let idx = this.hash(key);
let value = this.hashMap[idx].get(key);
if(value) {
return console.log('RETRIEVED: ' + value);
}
return null;
}
}
// Instantiate a new hash table with a size of 10;
const myHashTable = new HashTable(10);
// Let pretends in a game when we reach a certain level, we get a reward. And this hashtable stores the rewards and levels needed.
// Inserting
myHashTable.insert("level-1", 'shortsword');
myHashTable.insert("level-5", 'longsword');
myHashTable.insert("level-9", 'poisen arrows');
// Print out the table
console.log(myHashTable);
// Removing
myHashTable.remove("level-1");
// Print out the table
console.log(myHashTable);
// Retrieving
myHashTable.retrieve("level-5");
myHashTable.retrieve("level-1");
// Print out the table
console.log(myHashTable);
Jarett Sisk