The Object keys() method

Object.keys() returns an array containing an object’s own enumerable string property names.

const car = {
  color: 'blue',
  brand: 'Ford',
  model: 'Fiesta'
}

Object.keys(car) //['color', 'brand', 'model']

You can use the result with any array operation:

for (const key of Object.keys(car)) {
  console.log(key, car[key])
}

See the MDN Object.keys() reference and the ECMAScript specification for the exact enumeration order and coercion rules.

Which properties are included?

Object.keys() only includes properties that are:

• owned directly by the object
• enumerable
• keyed by strings

It leaves out inherited properties, non-enumerable properties, and Symbol-keyed properties:

const id = Symbol('id')
const vehicle = { wheels: 4 }
const car = Object.create(vehicle)

car.brand = 'Ford'
car[id] = 123

Object.defineProperty(car, 'serialNumber', {
  value: 'ABC123',
  enumerable: false
})

Object.keys(car) //['brand']

Use these related methods when you need different data:

• Object.values() returns the corresponding values
• Object.entries() returns [key, value] pairs
• Object.getOwnPropertyNames() also includes non-enumerable string keys
• Object.getOwnPropertySymbols() returns own Symbol keys

Strings are converted to wrapper objects, so their character indexes are returned:

Object.keys('hello') //['0', '1', '2', '3', '4']

Passing null or undefined throws a TypeError.

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