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
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
其他回答
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。
注意:
Several years ago, I had implemented the following hashtable, which has had some features that were missing to the Map class. However, that's no longer the case — now, it's possible to iterate over the entries of a Map, get an array of its keys or values or both (these operations are implemented copying to a newly allocated array, though — that's a waste of memory and its time complexity will always be as slow as O(n)), remove specific items given their key, and clear the whole map. Therefore, my hashtable implementation is only useful for compatibility purposes, in which case it'd be a saner approach to write a proper polyfill based on this.
function Hashtable() {
this._map = new Map();
this._indexes = new Map();
this._keys = [];
this._values = [];
this.put = function(key, value) {
var newKey = !this.containsKey(key);
this._map.set(key, value);
if (newKey) {
this._indexes.set(key, this.length);
this._keys.push(key);
this._values.push(value);
}
};
this.remove = function(key) {
if (!this.containsKey(key))
return;
this._map.delete(key);
var index = this._indexes.get(key);
this._indexes.delete(key);
this._keys.splice(index, 1);
this._values.splice(index, 1);
};
this.indexOfKey = function(key) {
return this._indexes.get(key);
};
this.indexOfValue = function(value) {
return this._values.indexOf(value) != -1;
};
this.get = function(key) {
return this._map.get(key);
};
this.entryAt = function(index) {
var item = {};
Object.defineProperty(item, "key", {
value: this.keys[index],
writable: false
});
Object.defineProperty(item, "value", {
value: this.values[index],
writable: false
});
return item;
};
this.clear = function() {
var length = this.length;
for (var i = 0; i < length; i++) {
var key = this.keys[i];
this._map.delete(key);
this._indexes.delete(key);
}
this._keys.splice(0, length);
};
this.containsKey = function(key) {
return this._map.has(key);
};
this.containsValue = function(value) {
return this._values.indexOf(value) != -1;
};
this.forEach = function(iterator) {
for (var i = 0; i < this.length; i++)
iterator(this.keys[i], this.values[i], i);
};
Object.defineProperty(this, "length", {
get: function() {
return this._keys.length;
}
});
Object.defineProperty(this, "keys", {
get: function() {
return this._keys;
}
});
Object.defineProperty(this, "values", {
get: function() {
return this._values;
}
});
Object.defineProperty(this, "entries", {
get: function() {
var entries = new Array(this.length);
for (var i = 0; i < entries.length; i++)
entries[i] = this.entryAt(i);
return entries;
}
});
}
Hashtable类的文档
方法:
(关键) 返回与指定键相关联的值。 参数: key:从中检索值的键。
put(关键字,值) 将指定的值关联到指定的键。 参数: key:与值相关联的键。 value:与键相关联的值。
remove(键) 删除指定的键以及与之关联的值。 参数: key:要移除的键。
clear () 清除整个哈希表，通过删除其所有条目。
indexOfKey(关键) 返回指定键的索引，根据已添加的订单项。 参数: key:获取索引的键。
indexOfValue(值) 返回指定值的索引，根据已添加的订单项。 参数: value:要获取索引的值。 备注: 价值是根据身份进行比较的。
entryAt(索引) 返回一个具有键和值属性的对象，表示指定索引处的条目。 参数: index:要获取的条目的索引。
containsKey(关键) 返回哈希表是否包含指定的键。 参数: 钥匙:要找的钥匙。
containsValue(值) 返回哈希表是否包含指定的值。 参数: value:要查找的值。
forEach(迭代器) 遍历哈希表中的所有条目，调用指定的迭代器。 参数: iterator:具有三个参数:key、value和index的方法，其中index根据条目被添加的顺序表示条目的索引。
属性:
长度(只读) 获取哈希表中条目的计数。 键(只读) 获取哈希表中所有键的数组。 值(只读) 获取哈希表中所有值的数组。 条目(只读) 获取哈希表中所有项的数组。它们的表示方式与entryAt()方法相同。
function HashTable() {
this.length = 0;
this.items = new Array();
for (var i = 0; i < arguments.length; i += 2) {
if (typeof (arguments[i + 1]) != 'undefined') {
this.items[arguments[i]] = arguments[i + 1];
this.length++;
}
}
this.removeItem = function (in_key) {
var tmp_previous;
if (typeof (this.items[in_key]) != 'undefined') {
this.length--;
var tmp_previous = this.items[in_key];
delete this.items[in_key];
}
return tmp_previous;
}
this.getItem = function (in_key) {
return this.items[in_key];
}
this.setItem = function (in_key, in_value) {
var tmp_previous;
if (typeof (in_value) != 'undefined') {
if (typeof (this.items[in_key]) == 'undefined') {
this.length++;
} else {
tmp_previous = this.items[in_key];
}
this.items[in_key] = in_value;
}
return tmp_previous;
}
this.hasItem = function (in_key) {
return typeof (this.items[in_key]) != 'undefined';
}
this.clear = function () {
for (var i in this.items) {
delete this.items[i];
}
this.length = 0;
}
}
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
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 */
}
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