What are the valid characters/values allowed as “keys” in javascript object? [duplicate]

Question

: ：

Which characters are valid/invalid in a JSON key name? (4 answers)

Closed 7 months ago .

I tried a few of them,

const obj = {
    '`' : 1,
    '@' : 2,
    '^' : 3,
    '-' : 4,
    '?' : 5,
    ']' : 6,
    '*' : 8,
    ')' : 9,
    '/' : 10,
    '>' : 11,
    'ル': 12
}

console.log(obj); //{ '`': 1, '@': 2, '^': 3,'-': 4, '?': 5, ']': 6, '*': 8, ')': 9, '/': 10, '>': 11, 'ル': 12}

So my question is, what is that superset of characters(individually not a combination of them, which obviously, would be silly to ask) which can qualify as a key in an JavaScript object?

EDITED ----

I've had people comparing JSON with JavaScript objects and deriving answers from them. I do understand Which characters are valid/invalid in a JSON key name? has some good insights.

But to touch upon whether a few things are allowed or disallowed wrt comparison between JSON and JavaScript "keys" purely keeping in mind whether those keys are allowed to be typed in or not , how about null , undefined ?

I'm not getting into how they are internally coerced and inserted as keys or what coercion takes place while retrieving the value using the brackets [ ] notation. Purely based on whether you are allowed to type in that value or not, yes there is a difference between which keys are allowed in JSON vs what is allowed in JavaScript object .

null as key in JavaScript object

let x = {null: 10};
for(let key in x){
    console.log(key); //null
    console.log(typeof key); //string
}

Works

null as key in JSON

{
    null: 10
}

Doesn't work

Answer 1

Any string is allowed as an object key. From the spec :

Properties are identified using key values. A property key value is either an ECMAScript String value or a Symbol value. All String and Symbol values, including the empty String, are valid as property keys. A property name is a property key that is a String value.