How to Get a JavaScript Object’s Property Names?

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Sometimes, we want to get the names of the properties in a JavaScript object.

In this article, we’ll look at how to get a JavaScript object’s property names with JavaScript.

We can use the Object.keys method to return an array of property name strings.

For instance, we can write:

const obj = {
  a: 1,
  b: 2,
  c: 3
}
Object.keys(obj).forEach(key => {
  console.log(key)
  console.log(obj[key])
})

We created the obj object with properties a , b , and c .

Then we call Object.keys with obj to return the property names of obj as strings.

Then we call forEach with a callback that has the key parameter with the key of the object being iterated through.

In the callback, we log the key and the value which we access with obj[key] .

Therefore, we get:

a
1
b
2
c
3

as the result.

We can get the object keys with the for-in loop.

For instance, we can write:

const obj = {
  a: 1,
  b: 2,
  c: 3
}
for (const key in obj) {
  console.log(key);
  console.log(obj[key]);
}

We get the object key from the key loop variable.

And then we get the key and value within the loop body the same way.

Therefore, we get:

a
1
b
2
c
3

as the result just like the previous example.

The for-in loop also loops through any properties inherited from prototype objects so we may get more keys than from the Object.keys method.

Object.keys only get property keys from non-inherited properties.

We can use the Object.keys method or the for-in loop to get the keys from a JavaScript object.

By John Au-Yeung