Hash Table implementation in JavaScript

hashTable.js

var HashTable = function() {
  this._limit = 8; // choose any size of hash table bucket limit
  this._count = 0;
  this._storage = [];
};

HashTable.prototype.insert = function(k, v) {
  var i = this._getHashIndex(k, this._limit);
  this._checkLimit(i); // make sure hashidx is in bounds
  var bucket = this._storage[i];

  if (!bucket) {
    this._storage[i] = [];
  }

  var found = false;

  for (var i = 0; i < bucket.length; i++) {
    var tuple = bucket[i];
    
    // found matching key
    if (tuple[0] === k) {
      // update key with new value
      tuple[1] = v;
      found = true;
      break;
    }
  }

  // no matching key found
  if (!found) {
    bucket.push([k,v]);
    this._count++;
    if (this._count > this._limit * 0.75) {
      this._resize(this._limit * 2);
    }
  }
};

HashTable.prototype.retrieve = function(k) {
  var i = this._getHashIndex(k, this._limit);
  this._checkLimit(i);
  var bucket = this._storage[i];
  
  if (!bucket) {
    return null;
  }
  
  for (var j = 0; j < bucket.length; j++) {
    var tuple = bucket[j];
    if (tuple[0] === k) {
      return tuple[1];
    }
  }
  
  return null;
};

HashTable.prototype.remove = function(k) {
  var i = this._getHashIndex(k, this._limit);
  this._checkLimit(i);
  var bucket = this._storage[i];

  if (!bucket) {
    return null;
  }

  for (var j = 0; j < bucket.length; j++) {
    var tuple = bucket[j];
    if (tuple[0] === k) {
      bucket.splice(j, 1);
      this._count--;
      if (this._count < this._limit * 0.25) {
        this._resize(this._limit / 2);
      }
      return tuple[1];
    }
  }
  
  return null;
};

// private methods _

HashTable.prototype._resize = function(newLimit) {
  var oldStorage = this._storage;
  this._storage = [];
  this._limit = newLimit;
  this._count = 0;

  for (var j = 0; j < oldStorage.length; j++) {
    var bucket = oldStorage[j];
    if (!bucket) break;
    
    for (var i = 0; i < bucket.length; i++) {
      var tuple = bucket[i];
      this.insert(tuple[0], tuple[1]);
    }
  }
};

HashTable.prototype._getHashIndex = function(str, max) {
  var hash = 0;
  for (var i = 0; i < str.length; i++) {
    hash = (hash<<5) + hash + str.charCodeAt(i);
    hash = hash & hash;
    hash = Math.abs(hash);
  }
  
  return hash % max;
};

HashTable.prototype._checkLimit = function(index) {
  if (typeof index !== 'number') {
    throw new Error('first argument of setter must be a numeric index');
  }
  if (limit <= index) {
    throw new Error('out-of-bounds index cannot be accessed');
  }
};