有没有办法使用数字类型作为对象键？

It seems that when I use a numeric type as a key name in an object, it always gets converted to a string. Is there anyway to actually get it to store as a numeric? The normal typecasting does not seem to work.

似乎当我在对象中使用数字类型作为键名时，它总是被转换为字符串。反正有没有把它作为数字存储？正常的类型转换似乎不起作用。

Example:

例：

var userId = 1;
console.log( typeof userId ); // number
myObject[userId] = 'a value';
console.dir(myObject);

Dir Output:

目录输出：

{
    '1': 'a value'
}

What I want is this:

我想要的是这个：

{
    1: 'a value'
}

Advice?

建议吗？

Thanks

谢谢

5 个解决方案

#1

No, this is not possible. The key will always be converted to a string. See Property Accessor docs

不，这是不可能的。密钥将始终转换为字符串。请参阅属性访问者文档

Property names must be strings. This means that non-string objects cannot be used as keys in the object. Any non-string object, including a number, is typecasted into a string via the toString method.

属性名称必须是字符串。这意味着非字符串对象不能用作对象中的键。任何非字符串对象（包括数字）都通过toString方法被类型化为字符串。

> var foo = {}
undefined

> foo[23213] = 'swag'
'swag'

> foo
{ '23213': 'swag' }

> typeof(Object.keys(foo)[0])
'string'

#2

In an object, no, but I have found Map extremely useful for this application. Here is where I have used it for numeric keys, a key-based event.

在一个对象中，没有，但我发现Map对此应用程序非常有用。这是我用它来做数字键的地方，这是一个基于键的事件。

onKeydown(e) {
  const { toggleSidebar, next, previous } = this.props;

  const keyMapping = new Map([
    [ 83, toggleSidebar ],  // user presses the s button
    [ 37, next          ],  // user presses the right arrow
    [ 39, previous      ]   // user presses the left arrow
  ]);

  if (keyMapping.has(e.which)) {
    e.preventDefault();
    keyMapping.get(e.which)();
  }
}

#3

Appears to be by design in ECMA-262-5:

看似ECMA-262-5的设计：

The Property Identifier type is used to associate a property name with a Property Descriptor. Values of the Property Identifier type are pairs of the form (name, descriptor), where name is a String and descriptor is a Property Descriptor value.

属性标识符类型用于将属性名称与属性描述符相关联。属性标识符类型的值是形式（名称，描述符）的对，其中name是String，描述符是Property Descriptor值。

However, I don't see a definite specification for it in ECMA-262-3. Regardless, I wouldn't attempt to use non-strings as property names.

但是，我在ECMA-262-3中没有看到明确的规格。无论如何，我不会尝试使用非字符串作为属性名称。

#4

I think you can do the following if you want to use the above thing for accessing it like as a number, I did the same and worked.

我想你可以做以下事情，如果你想使用上面的东西来访问它，就像一个数字，我做了同样的工作。

var myObj = {"0":"a","1":"b","CNT":2};
$.each(myObj,function(key,value){
     if(isNaN(parseInt(key))){
          return true; //continue;
     }
     //Code to perform operation
}

This works only when the key doesn't start with and numeric character otherwise it'll be converted to a number. See the following example:

这仅在键不以数字字符开头时才起作用，否则它将被转换为数字。请参阅以下示例：

parseInt("45kjghk") === 45

I used jQuery here

我在这里使用jQuery

Updated:

更新：

var myObj = {"0":"a","1":"b","CNT":2};
$.each(myObj,function(key,value){
     if(isNaN(parseInt(key)) || (key.length !== parseInt(key).toString().length) ){
          return true; //continue;
     }
     //Code to perform operation
}

It may overcome the above problem. Please suggest better if available and problem with this answer if there are.

它可以克服上述问题。如果有的话，请建议更好（如果有的话）和问题。

#5

-2

In JavaScript, numerical strings and numbers are interchangeable, so

在JavaScript中，数字字符串和数字是可以互换的

myObject[1] == myObject['1']

If you really want number to be the key for an object, you might want an array (i.e. created with new Array() or []).

如果您确实希望number为对象的键，则可能需要一个数组（即使用new Array（）或[]创建）。

#1