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?
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
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)
其他回答
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 = {};
在c#中,代码如下:
Dictionary<string,int> dictionary = new Dictionary<string,int>();
dictionary.add("sample1", 1);
dictionary.add("sample2", 2);
or
var dictionary = new Dictionary<string, int> {
{"sample1", 1},
{"sample2", 2}
};
在JavaScript中:
var dictionary = {
"sample1": 1,
"sample2": 2
}
c#字典对象包含有用的方法,如dictionary. containskey ()
在JavaScript中,我们可以像这样使用hasOwnProperty:
if (dictionary.hasOwnProperty("sample1"))
console.log("sample1 key found and its value is"+ dictionary["sample1"]);
所有现代浏览器都支持JavaScript Map对象。有几个原因使得使用Map比使用Object更好:
Object有一个原型,所以映射中有默认键。 对象的键是字符串,它们可以是Map的任何值。 当你必须跟踪对象的大小时,你可以很容易地获得Map的大小。
例子:
var myMap = new Map();
var keyObj = {},
keyFunc = function () {},
keyString = "a string";
myMap.set(keyString, "value associated with 'a string'");
myMap.set(keyObj, "value associated with keyObj");
myMap.set(keyFunc, "value associated with keyFunc");
myMap.size; // 3
myMap.get(keyString); // "value associated with 'a string'"
myMap.get(keyObj); // "value associated with keyObj"
myMap.get(keyFunc); // "value associated with keyFunc"
如果希望垃圾收集没有从其他对象引用的键,可以考虑使用WeakMap而不是Map。
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
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。