Get object property name as a string

Question

Is it possible to get the object property name as a string

person = {};
person.first_name = \'Jack\';
person.last_name = \'Trades\';
person.address = {};
per         


        

Answer 1

You can accomplish this by converting all object properties into functions which will return the their own names

var person = {};
person.firstname = 'Jack';
person.address = "123 Street";

function getPropertyName(obj, expression) {
    var res = {};
    Object.keys(obj).map(k => { res[k] = () => k; });
    return expression(res)();
}

let result = getPropertyName(person, o => o.address);
console.log(result); // Output: 'address'

Answer 2

I know a best practice that using Object.keys(your_object). It will parse to array property name for you. Example:

var person = { firstName: 'John', lastName: 'Cena', age: '30' };
var listPropertyNames = Object.keys(person); //["firstName", "lastName", "age"]

I hope this example is useful for you.

Answer 3

You can wrap your property in a function and then convert the function to a string and get the property out of it.

For example:

function getPropertyName(propertyFunction) {
    return /\.([^\.;]+);?\s*\}$/.exec(propertyFunction.toString())[1];
}

Then to use it:

var myObj = {
    myProperty: "testing"
};

getPropertyName(function() { myObj.myProperty; }); // myProperty

Beware that minifiers could break this.

Edit: I have created a compiler transform that works with babel and the typescript compiler (see ts-nameof). This is a much more reliable than doing something at runtime.

Answer 4

No, it's not possible.

Imagine this:

person.age = 42;
person.favoriteNumber = 42;

var pn = propName(person.age)
// == propName(42)
// == propName(person.favoriteNumber);

The reference to the property name is simply lost in that process.

Answer 5

Yes you can, with a little change.

function propName(prop, value){
   for(var i in prop) {
       if (prop[i] == value){
            return i;
       }
   }
   return false;
}

Now you can get the value like so:

 var pn = propName(person,person.first_name);
 // pn = "first_name";

Note I am not sure what it can be used for.

Other Note wont work very well with nested objects. but then again, see the first note.

Answer 6

I like one liners, here's a generic solution:

const propName = (obj,type) => Object.keys(obj).find(key => obj[key] === type)

propName(person, person.age)