“JavaScript Hashtable” Kod odpowiedzi

Hashtable JS

// 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

JavaScript Hashtable

//  JavaScript's Object type is a special hash table
// The most common example of a Hash Table in JavaScript is the Object data type, 
// where you can pair the object's property value with a property key.

In the following example, the likes object contain what people like by having their
name "John" as Key and "Playing Football"  as the value.

let likes = {
  John: "Playing Football",
  Jane: "Watching Soap Operas"
}

More details
https://www.freecodecamp.org/news/javascript-hash-table-associative-array-hashing-in-js/
Smiling Starling

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