Is there any way to use a numeric type as an object key?

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.

Example:

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

Dir Output:

{
    '1': 'a value'
}

What I want is this:

{
    1: 'a value'
}

Advice?

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

> 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.

> var foo = {}
undefined

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

> foo
{ '23213': 'swag' }

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

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.

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)();
  }
}

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

>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.

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.

Here is the solution. Please tell me the environmental setups if this is not working

const screens = {
    "768": "large",
    "200": "small"
}

const keys = Object.keys(screens).map(key => parseInt(key))
                                         // OR Number(key)

console.log(keys) // Output [200, 768]

Do we need something like this?

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

Console: Object

1 : "a value"

you can use, Map if you want different datatype as keys

const map1 = new Map();

map1.set(1,3)
map1.set('1','string')

// expected output: 3

console.log(map1.get(1)) //output 3;
console.log(map1.get('1')) //output 'string';

Per Mozilla: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax[Spread syntax]1

let obj1 = { foo: 'bar', x: 42 };
let obj2 = { foo: 'baz', y: 13 };
const merge = ( ...objects ) => ( { ...objects } );

let mergedObj1 = merge (obj1, obj2);
// Object { 0: { foo: 'bar', x: 42 }, 1: { foo: 'baz', y: 13 } }

let mergedObj2 = merge ({}, obj1, obj2);
// Object { 0: {}, 1: { foo: 'bar', x: 42 }, 2: { foo: 'baz', y: 13 } }

Just order the items before hand and you should get the result you want.

So for your case:

const merge = (...objects) => ({...objects});

//An object with numeric keys
const values = ["a value", "another value", "and another value"];
        
let merged = merge(...values);

console.log(merged);

You can try this:

arr = {}
function f(a,b,c) {
      arr = arguments
}
f("*","#","_")
console.log(arr)
//returns Object { 0: "*", 1: "#", 2: "_" }```

In JavaScript, numerical strings and numbers are interchangeable, so

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 []).