How to extract exact union type from object key strings in typescript?

Question

I've got an object like this

const MY_OBJECT = {
  'key': 'key val',
  'anotherKey': 'anotherKey val',
};

Is there a way to extract from this object 'key' | 'anotherKey' 'key' | 'anotherKey' type ?

Answer 1

To get a type that is a union keys of a variable you need to use keyof typeof variableName .

const MY_OBJECT = {
    'key': 'key val',
    'anotherKey': 'anotherKey val',
};
type MY_OBJECT_KEYS = keyof typeof MY_OBJECT // "key" | "anotherKey"

Answer 2

to achieve what you are looking for you just have to get rid of quotation marks in your object:

const MY_OBJECT = {
  key: 'key val',
  anotherKey: 'anotherKey val',
};
console.log(keyof MY_OBJECT); // "key" | "anotherKey"