Copy original array with empty values

February 13, 2022

I have the following array:

arr1 = [{Name: "John", Email: "john@example.com", Age: "29"}, {Name: "Emma", Email: "emma@example.com", Age: "25"}]

How can I get this array as:

arr2 = [{Name: "", Email: "", Age: ""}]

without mutating arr1

I have tried doing:

let arr2 = arr1[0]

for (let i in arr2) {
    arr2[i] = ""
}

console.log(arr1) //returns [{Name: "", Email: "", Age: ""}, {Name: "Emma", Email: "emma@example.com", Age: "25"}]
console.log(arr2) //returns [{Name: "", Email: "", Age: ""}]

but this mutates arr1[0] with empty values as well

I have searched a lot of questions on SO, but couldn’t get anything that would set all the values empty.

>Solution :

You’re passing by reference instead of copying the array.

https://dmitripavlutin.com/value-vs-reference-javascript/#:~:text=In%20JavaScript%2C%20you%20can%20pass,by%20reference%20when%20assigning%20objects.

Here’s your code refactored to work as intended.

arr1 = [{Name: "John", Email: "john@example.com", Age: "29"}, {Name: "Emma", Email: "emma@example.com", Age: "25"}]
let arr2 = {...arr1[0]} // make a copy of arr1[0]

for (let i in arr2) {
    arr2[i] = ""
}

console.log(arr1) //returns [{Name: "", Email: "", Age: ""}, {Name: "Emma", Email: "emma@example.com", Age: "25"}]
console.log([arr2]) //returns [{Name: "", Email: "", Age: ""}]