How to Duplicate JavaScript Object Properties in JavaScript Another Object?

Oftentimes, we may want to duplicate a JavaScript object’s properties into another object.

In this article, we’ll look at how to duplicate JavaScript object properties in another JavaScript object.

Using the Object.assign Method

One way to duplicate an object’s properties in another object is to use the Object.assign method.

For instance, we can write:

const firstObject = {
  a: 1,
  b: 2
}
const secondObject = {
  c: 3
}
Object.assign(secondObject, firstObject);
console.log(secondObject)

We have the firstObject and secondObject objects with some properties.

Then we call Object.assign to copy the properties of the firstObject object into the secondObject .

Therefore, from the console log, we see that secondObject is:

{c: 3, a: 1, b: 2}

after we call Object.assign .

If we don’t want to modify secondObject , we can write:

const firstObject = {
  a: 1,
  b: 2
}
const secondObject = {
  c: 3
}
const thirdObject = Object.assign({}, firstObject, secondObject)
console.log(thirdObject)

Then thirdObject is:

{a: 1, b: 2, c: 3}

and secondObject is unmodified.

Spread Operator

Another way to copy an object’s property into another object is to use the spread operator.

For instance, we can write:

const firstObject = {
  a: 1,
  b: 2
}
const secondObject = {
  c: 3
}
const thirdObject = {
  ...firstObject,
  ...secondObject
}
console.log(thirdObject)

We created a thirdObject object which is created from spreading the properties of firstObject and secondObject into it.

Therefore, thirdObject is:

{a: 1, b: 2, c: 3}

Conclusion

We can use the Object.assign method or the spread operator to copy properties from one object onto another.