The HashTable Class in Javascript

Web DevelopmentFront End TechnologyJavascript

Here is the complete implementation of the HashTable class. This could of course be improved by using more efficient data structures and collision resolution algorithms.

Example


class HashTable {
   constructor() {
      this.container = [];
      // Populate the container with empty arrays
      // which can be used to add more elements in
      // cases of collisions
      for (let i = 0; i < 11; i++) {
         this.container.push([]);
      }
   }

   display() {
      this.container.forEach((value, index) => {
         let chain = value
         .map(({ key, value }) => `{ ${key}: ${value} }`)
         .join(" --> ");
         console.log(`${index}: ${chain}`);
      });
   }

put(key, value) {
   let hashCode = this.hash(key);

   for (let i = 0; i < this.container[hashCode].length; i++) {
      // Replace the existing value with the given key
      // if it already exists
      if (this.container[hashCode][i].key === key) {
         this.container[hashCode][i].value = value;
         return;
      }
   }

   // Push the pair at the end of the array
   this.container[hashCode].push(new this.KVPair(key, value));
}

get(key) {
   let hashCode = this.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;
}

remove(key) {
   let hashCode = this.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) {
         this.container[hashCode].splice(i, 1);
         return true;
      }
   }
   return false;
}

hash(key) {
   return key % 11;
}
forEach(callback) {
   // For each chain
   this.container.forEach(elem => {
      // For each element in each chain call callback on KV pair
      elem.forEach(({ key, value }) => callback(key, value));
      });
   }

   static join(table1, table2) {
      // Check if both args are HashTables
      if (!table1 instanceof HashTable || !table2 instanceof HashTable) {
         throw new Error("Illegal Arguments");
      }

      let combo = new HashTable();
      table1.forEach((k, v) => combo.put(k, v));
      table2.forEach((k, v) => combo.put(k, v));
      return combo;
   }
}

HashTable.prototype.KVPair = class {
   constructor(key, value) {
      this.key = key;
      this.value = value;
   }
};
raja
Published on 28-Jun-2018 07:20:46
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