JavaScript中有哈希代码函数吗?-IsthereanykindofhashcodefunctioninJavaScript?

32  

The easiest way to do this is to give each of your objects its own unique toString method:

要做到这一点，最简单的方法就是给你的每个对象一个独特的toString方法:

(function() {
    var id = 0;

    /*global MyObject */
    MyObject = function() {
        this.objectId = '<#MyObject:' + (id++) + '>';
        this.toString= function() {
            return this.objectId;
        };
    };
})();

I had the same problem and this solved it perfectly for me with minimal fuss, and was a lot easier that re-implementing some fatty Java style Hashtable and adding equals() and hashCode() to your object classes. Just make sure that you don't also stick a string '<#MyObject:12> into your hash or it will wipe out the entry for your exiting object with that id.

我也遇到了同样的问题，这就很好地为我解决了这个问题，而且很容易重新实现一些胖Java风格的散列表，并向对象类添加equals()和hashCode()。只要确保您不将字符串'<#MyObject:12>插入到您的散列中，否则它将用该id清除退出对象的条目。

Now all my hashes are totally chill. I also just posted a blog entry a few days ago about this exact topic.

现在我所有的散列都是冷的。几天前，我刚刚就这个话题发表了一篇博客文章。

18  

The solution I chose is similar to Daniel's, but rather than use an object factory and override the toString, I explicitly add the hash to the object when it is first requested through a getHashCode function. A little messy, but better for my needs :)

我选择的解决方案与Daniel的类似，但我没有使用对象工厂并覆盖toString，而是在通过getHashCode函数首次请求对象时显式地将散列添加到对象中。有点乱，但更符合我的需要:)

Function.prototype.getHashCode = (function(id) {
    return function() {
        if (!this.hashCode) {
            this.hashCode = '';
        }
        return this.hashCode;
    }
}(0));

16  

What you described is covered by Harmony WeakMaps, part of the ECMAScript 6 specification (next version of Javascript). That is: a set where the keys can be anything (including undefined) and is non-enumerable.

您所描述的是Harmony WeakMaps，它是ECMAScript 6规范(Javascript的下一个版本)的一部分。即:一个集合，其中的键可以是任何东西(包括未定义的)，并且是不可枚举的。

This means it's impossible to get a reference to a value unless you have a direct reference to the key (any object!) that links to it. It's important for a bunch of engine implementation reasons relating to efficiency and garbage collection, but it's also super cool for in that it allows for new semantics like revokable access permissions and passing data without exposing the data sender.

这意味着不可能获得对值的引用，除非您有指向该值的键(任何对象!)的直接引用。对于与效率和垃圾收集相关的许多引擎实现原因来说，这很重要，但它也非常酷，因为它允许新的语义，比如撤销访问权限和传递数据，而不暴露数据发送者。

From MDN:

中数:

var wm1 = new WeakMap(),
    wm2 = new WeakMap();
var o1 = {},
    o2 = function(){},
    o3 = window;

wm1.set(o1, 37);
wm1.set(o2, "azerty");
wm2.set(o1, o2); // A value can be anything, including an object or a function.
wm2.set(o3, undefined);
wm2.set(wm1, wm2); // Keys and values can be any objects. Even WeakMaps!

wm1.get(o2); // "azerty"
wm2.get(o2); // Undefined, because there is no value for o2 on wm2.
wm2.get(o3); // Undefined, because that is the set value.

wm1.has(o2); // True
wm2.has(o2); // False
wm2.has(o3); // True (even if the value itself is 'undefined').

wm1.has(o1);   // True
wm1.delete(o1);
wm1.has(o1);   // False

WeakMaps are available in current Firefox, Chrome and Edge. They're also supported in Node v7 , and in v6 with the --harmony-weak-maps flag.

弱地图可以在当前的Firefox、Chrome和Edge中使用。它们在节点v7中也得到了支持，在v6中也有—谐波-弱映射标志。

8  

For my specific situation I only care about the equality of the object as far as keys and primitive values go. The solution that worked for me was converting the object to its JSON representation and using that as the hash. There are limitations such as order of key definition potentially being inconsistent; but like I said it worked for me because these objects were all being generated in one place.

对于我的具体情况，我只关心键和原始值之间的相等性。我的解决方案是将对象转换为JSON表示，并将其用作散列。有一些限制，比如关键定义的顺序可能不一致;但就像我说的，它对我有用因为这些对象都是在一个地方生成的。

var hashtable = {};

var myObject = {a:0,b:1,c:2};

var hash = JSON.stringify(myObject);
// '{"a":0,"b":1,"c":2}'

hashtable[hash] = myObject;
// {
//   '{"a":0,"b":1,"c":2}': myObject
// }

8  

The Javascript specification defines indexed property access as performing a toString conversion on the index name. For example,

Javascript规范将索引属性访问定义为对索引名执行toString转换。例如,

myObject[myProperty] = ...;

is the same as

是一样的

myObject[myProperty.toString()] = ...;

This is necessary as in Javascript

这是必需的，就像在Javascript中一样

myObject["someProperty"]

is the same as

是一样的

myObject.someProperty

And yes, it makes me sad as well :-(

是的，这也让我难过

8  

I put together a small Javascript module a while ago to produce hashcodes for strings, objects, arrays, etc. (I just committed it to GitHub :) )

我不久前组装了一个小的Javascript模块，为字符串、对象、数组等生成hashcode(我只是将它提交给GitHub:)。

Usage:

用法:

Hashcode.value("stackoverflow")
// -2559914341
Hashcode.value({ 'site' : "stackoverflow" })
// -3579752159

6  

In ECMAScript 6 there's now a Set that works how you'd like: https://developer.mozilla.org/en-US/docs/Web/Javascript/Reference/Global_Objects/Set

在ECMAScript 6中，现在有一个设置可以按照您的要求工作:https://developer.mozilla.org/en-US/docs/Web/Javascript/Reference/Global_Objects/Set

It's already available in the latest Chrome, FF, and IE11.

它已经在最新的Chrome、FF和IE11中可用。

3  

Reference: https://developer.mozilla.org/en-US/docs/Web/Javascript/Reference/Global_Objects/Symbol

参考:https://developer.mozilla.org/en-US/docs/Web/Javascript/Reference/Global_Objects/Symbol

you can use Es6 symbol to create unique key and access object. Every symbol value returned from Symbol() is unique. A symbol value may be used as an identifier for object properties; this is the data type's only purpose.

您可以使用Es6符号来创建唯一的密钥和访问对象。从symbol()返回的每个符号值都是惟一的。符号值可以用作对象属性的标识符;这是数据类型的唯一用途。

var obj = {};

obj[Symbol('a')] = 'a';
obj[Symbol.for('b')] = 'b';
obj['c'] = 'c';
obj.d = 'd';

1  

My solution introduces a static function for the global Object object.

我的解决方案为全局对象对象引入了一个静态函数。

(function() {
    var lastStorageId = 0;

    this.Object.hash = function(object) {
        var hash = object.__id;

        if (!hash)
             hash = object.__id = lastStorageId++;

        return '#' + hash;
    };
}());

I think this is more convenient with other object manipulating functions in Javascript.

我认为在Javascript中使用其他对象操作函数更方便。

1  

Here's my simple solution that returns a unique integer.

下面是返回唯一整数的简单解决方案。

function hashcode(obj) {
    var hc = 0;
    var chars = JSON.stringify(obj).replace(/\{|\"|\}|\:|,/g, '');
    var len = chars.length;
    for (var i = 0; i