// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/create-a-hash-table

var called = 0;
var hash = (string) => {
  called++;
  var hashed = 0;
  for (var i = 0; i < string.length; i++) {
    hashed += string.charCodeAt(i);
  }
  return hashed;
};
var HashTable = function () {
  this.collection = {};
  // Only change code below this line
  this.add = (k, v) => {
    const keyHash = hash(k);
    if (this.collection[keyHash] === undefined) {
      this.collection[keyHash] = [[k, v]];
    } else {
      this.collection[keyHash].push([k, v]);
    }
  };

  this.remove = (k) => {
    const keyHash = hash(k);
    if (this.collection[keyHash] === undefined) {
      return;
    }
    this.collection[keyHash] = this.collection[keyHash].filter(
      ([key, value]) => key !== k
    );
    if (this.collection[keyHash].length === 0) {
      delete this.collection[keyHash];
    }
  };

  this.lookup = (k) => {
    const keyHash = hash(k);
    if (this.collection[keyHash] === undefined) {
      return null;
    }
    for (let [key, value] of this.collection[keyHash]) {
      if (key === k) {
        return value;
      }
    }
    return null;
  };
  // Only change code above this line
};