我需要使用JavaScript存储一些统计数据,就像我在c#中做的那样:

Dictionary<string, int> statistics;

statistics["Foo"] = 10;
statistics["Goo"] = statistics["Goo"] + 1;
statistics.Add("Zoo", 1);

JavaScript中是否存在哈希表或Dictionary<TKey, TValue>之类的东西? 我如何以这种方式存储值呢?


当前回答

使用JavaScript对象作为关联数组。

关联数组:简单地说,关联数组使用字符串而不是整数作为索引。

使用

var dictionary = {};

JavaScript允许您使用以下语法向对象添加属性:

Object.yourProperty = value;

相同的另一种语法是:

Object["yourProperty"] = value;

如果可以,也可以使用以下语法创建键到值的对象映射:

var point = { x:3, y:2 };

point["x"] // returns 3
point.y // returns 2

可以使用for..in循环构造遍历关联数组,如下所示

for(var key in Object.keys(dict)){
  var value = dict[key];
  /* use key/value for intended purpose */
}

其他回答

除非你有特别的理由不这样做,否则就用一个普通的对象。JavaScript中的对象属性可以使用哈希表样式的语法引用:

var hashtable = {};
hashtable.foo = "bar";
hashtable['bar'] = "foo";

foo和bar元素现在都可以被引用为:

hashtable['foo'];
hashtable['bar'];

// Or
hashtable.foo;
hashtable.bar;

当然,这意味着你的键必须是字符串。如果它们不是字符串,它们会在内部转换为字符串,所以它仍然可以工作。你的里程可能会有所不同。

你可以像下面这样创建一个:

var字典={名字:“一些程序员”,年龄:24岁,工作:“编写程序”}; //使用键进行迭代 For (var key in dictionary) { console.log("Key: "+ Key + ", "+ "Value: "+ dictionary[Key]); } //使用对象表示法访问键: console.log(" she name is: " + dictionary.Name)

var associativeArray = {};
associativeArray["one"] = "First";
associativeArray["two"] = "Second";
associativeArray["three"] = "Third";

如果你来自面向对象的语言,你应该看看这篇文章。

由于JavaScript中的每个对象都像哈希表一样,并且通常是作为哈希表实现的,所以我就这样…

var hashSweetHashTable = {};

https://gist.github.com/alexhawkins/f6329420f40e5cafa0a4

var HashTable = function() {
  this._storage = [];
  this._count = 0;
  this._limit = 8;
}


HashTable.prototype.insert = function(key, value) {

  // Create an index for our storage location by passing
  // it through our hashing function
  var index = this.hashFunc(key, this._limit);

  // Retrieve the bucket at this particular index in
  // our storage, if one exists
  //[[ [k,v], [k,v], [k,v] ] , [ [k,v], [k,v] ]  [ [k,v] ] ]
  var bucket = this._storage[index]

  // Does a bucket exist or do we get undefined
  // when trying to retrieve said index?
  if (!bucket) {
    // Create the bucket
    var bucket = [];
    // Insert the bucket into our hashTable
    this._storage[index] = bucket;
  }

  var override = false;

  // Now iterate through our bucket to see if there are any conflicting
  // key value pairs within our bucket. If there are any, override them.
  for (var i = 0; i < bucket.length; i++) {
    var tuple = bucket[i];
    if (tuple[0] === key) {

      // Override value stored at this key
      tuple[1] = value;
      override = true;
    }
  }

  if (!override) {
    // Create a new tuple in our bucket.
    // Note that this could either be the new empty bucket we created above
    // or a bucket with other tupules with keys that are different than
    // the key of the tuple we are inserting. These tupules are in the same
    // bucket because their keys all equate to the same numeric index when
    // passing through our hash function.
    bucket.push([key, value]);
    this._count++

    // Now that we've added our new key/val pair to our storage
    // let's check to see if we need to resize our storage
    if (this._count > this._limit * 0.75) {
      this.resize(this._limit * 2);
    }
  }
  return this;
};


HashTable.prototype.remove = function(key) {
  var index = this.hashFunc(key, this._limit);
  var bucket = this._storage[index];
  if (!bucket) {
    return null;
  }

  // Iterate over the bucket
  for (var i = 0; i < bucket.length; i++) {
    var tuple = bucket[i];

    // Check to see if key is inside bucket
    if (tuple[0] === key) {

      // If it is, get rid of this tuple
      bucket.splice(i, 1);
      this._count--;
      if (this._count < this._limit * 0.25) {
        this._resize(this._limit / 2);
      }
      return tuple[1];
    }
  }
};


HashTable.prototype.retrieve = function(key) {
  var index = this.hashFunc(key, this._limit);
  var bucket = this._storage[index];

  if (!bucket) {
    return null;
  }

  for (var i = 0; i < bucket.length; i++) {
    var tuple = bucket[i];
    if (tuple[0] === key) {
      return tuple[1];
    }
  }

  return null;
};


HashTable.prototype.hashFunc = function(str, max) {
  var hash = 0;
  for (var i = 0; i < str.length; i++) {
    var letter = str[i];
    hash = (hash << 5) + letter.charCodeAt(0);
    hash = (hash & hash) % max;
  }
  return hash;
};


HashTable.prototype.resize = function(newLimit) {
  var oldStorage = this._storage;

  this._limit = newLimit;
  this._count = 0;
  this._storage = [];

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


HashTable.prototype.retrieveAll = function() {
  console.log(this._storage);
  //console.log(this._limit);
};

/******************************TESTS*******************************/

var hashT = new HashTable();

hashT.insert('Alex Hawkins', '510-599-1930');
//hashT.retrieve();
//[ , , , [ [ 'Alex Hawkins', '510-599-1930' ] ] ]
hashT.insert('Boo Radley', '520-589-1970');
//hashT.retrieve();
//[ , [ [ 'Boo Radley', '520-589-1970' ] ], , [ [ 'Alex Hawkins', '510-599-1930' ] ] ]
hashT.insert('Vance Carter', '120-589-1970').insert('Rick Mires', '520-589-1970').insert('Tom Bradey', '520-589-1970').insert('Biff Tanin', '520-589-1970');
//hashT.retrieveAll();
/*
[ ,
  [ [ 'Boo Radley', '520-589-1970' ],
    [ 'Tom Bradey', '520-589-1970' ] ],
  ,
  [ [ 'Alex Hawkins', '510-599-1930' ],
    [ 'Rick Mires', '520-589-1970' ] ],
  ,
  ,
  [ [ 'Biff Tanin', '520-589-1970' ] ] ]
*/

// Override example (Phone Number Change)
//
hashT.insert('Rick Mires', '650-589-1970').insert('Tom Bradey', '818-589-1970').insert('Biff Tanin', '987-589-1970');
//hashT.retrieveAll();

/*
[ ,
  [ [ 'Boo Radley', '520-589-1970' ],
    [ 'Tom Bradey', '818-589-1970' ] ],
  ,
  [ [ 'Alex Hawkins', '510-599-1930' ],
    [ 'Rick Mires', '650-589-1970' ] ],
  ,
  ,
  [ [ 'Biff Tanin', '987-589-1970' ] ] ]

*/

hashT.remove('Rick Mires');
hashT.remove('Tom Bradey');
//hashT.retrieveAll();

/*
[ ,
  [ [ 'Boo Radley', '520-589-1970' ] ],
  ,
  [ [ 'Alex Hawkins', '510-599-1930' ] ],
  ,
  ,
  [ [ 'Biff Tanin', '987-589-1970' ] ] ]


*/

hashT.insert('Dick Mires', '650-589-1970').insert('Lam James', '818-589-1970').insert('Ricky Ticky Tavi', '987-589-1970');
hashT.retrieveAll();


/* NOTICE HOW THE HASH TABLE HAS NOW DOUBLED IN SIZE UPON REACHING 75% CAPACITY, i.e. 6/8. It is now size 16.
 [,
  ,
  [ [ 'Vance Carter', '120-589-1970' ] ],
  [ [ 'Alex Hawkins', '510-599-1930' ],
    [ 'Dick Mires', '650-589-1970' ],
    [ 'Lam James', '818-589-1970' ] ],
  ,
  ,
  ,
  ,
  ,
  [ [ 'Boo Radley', '520-589-1970' ],
    [ 'Ricky Ticky Tavi', '987-589-1970' ] ],
  ,
  ,
  ,
  ,
  [ [ 'Biff Tanin', '987-589-1970' ] ] ]

*/

console.log(hashT.retrieve('Lam James'));  // 818-589-1970
console.log(hashT.retrieve('Dick Mires')); // 650-589-1970
console.log(hashT.retrieve('Ricky Ticky Tavi')); //987-589-1970
console.log(hashT.retrieve('Alex Hawkins')); // 510-599-1930
console.log(hashT.retrieve('Lebron James')); // null