Get the value of an object with an unknown single key in JS

Question

How can I get the value of an object with an unknown single key?

Example:

var obj = {dbm: -45}

I want to get the -45 value without

Answer 1

Object.keys might be a solution:

Object.keys({ dbm: -45}); // ["dbm"]

The differences between for-in and Object.keys is that Object.keys returns all own key names and for-in can be used to iterate over all own and inherited key names of an object.

As James Brierley commented below you can assign an unknown property of an object in this fashion:

var obj = { dbm:-45 };
var unkownKey = Object.keys(obj)[0];
obj[unkownKey] = 52;

But you have to keep in mind that assigning a property that Object.keys returns key name in some order of might be error-prone.

Answer 2

There's a new option now: Object.values. So if you know the object will have just one property:

const array = Object.values(obj)[0];

Live Example:

const json = '{"EXAMPLE": [ "example1","example2","example3","example4" ]}';
const obj = JSON.parse(json);
const array = Object.values(obj)[0];
console.log(array);

If you need to know the name of the property as well, there's Object.entries and destructuring:

const [name, array] = Object.entries(obj)[0];

Live Example:

const json = '{"EXAMPLE": [ "example1","example2","example3","example4" ]}';
const obj = JSON.parse(json);
const [name, array] = Object.entries(obj)[0];
console.log(name);
console.log(array);