How to create a copy of an array in Go or Golang?

Published September 2, 2022

To create a copy of an array in Go or golang, we can simply assign the array to another variable using the = operator (assignment) and the contents will be copied over to the new array variable.

TL;DR

package main

import "fmt"

func main(){
    // array of elements
    nums := [5]int{1, 2, 3, 4, 5}

    // copy the `nums` array elements to the
    // `numsCopy` using the `=` operator (assignment)
    numsCopy := nums

    // log to the elements of the
    // `numsCopy` variable to the console
    fmt.Println(numsCopy) // [1 2 3 4 5]

    // mutate the contents in the `numsCopy` array
    // to check to see if the contents in
    // the original array `nums` changes
    numsCopy[0] = 11

    // log both the `numsCopy` and `nums` array
    fmt.Println(numsCopy, nums) // [11 2 3 4 5] [1 2 3 4 5]
}

For example, let's say we have an array of 5 numbers like this,

package main

func main(){
    // array of elements
    nums := [5]int{1, 2, 3, 4, 5}
}

Now to copy the elements of the nums array we can define another variable called numsCopy and then use the = operator and then simply assign the values of the nums array to it.

It can be done like this,

package main

func main(){
    // array of elements
    nums := [5]int{1, 2, 3, 4, 5}

    // copy the `nums` array elements to the
    // `numsCopy` using the `=` operator (assignment)
    numsCopy := nums
}

Now to check if the numsCopy has the elements like in the nums variable, we can first print the numsCopy variable to the console using the Println() method from the fmt standard package like this,

package main

import "fmt"

func main(){
    // array of elements
    nums := [5]int{1, 2, 3, 4, 5}

    // copy the `nums` array elements to the
    // `numsCopy` using the `=` operator (assignment)
    numsCopy := nums

    // log to the elements of the
    // `numsCopy` variable to the console
    fmt.Println(numsCopy) // [1 2 3 4 5]
}

Now let's mutate the contents on the numsCopy array and see if the contents of the nums array change. It can be done like this,

package main

import "fmt"

func main(){
    // array of elements
    nums := [5]int{1, 2, 3, 4, 5}

    // copy the `nums` array elements to the
    // `numsCopy` using the `=` operator (assignment)
    numsCopy := nums

    // log to the elements of the
    // `numsCopy` variable to the console
    fmt.Println(numsCopy) // [1 2 3 4 5]

    // mutate the contents in the `numsCopy` array
    // to check to see if the contents in
    // the original array `nums` changes
    numsCopy[0] = 11

    // log both the `numsCopy` and `nums` array
    fmt.Println(numsCopy, nums) // [11 2 3 4 5] [1 2 3 4 5]
}

As you can see that the numsCopy array contents are changed but not the nums array content. This proves to us that the nums array is successfully copied into the numsCopy array variable. Yay 🥳!

See the above code live in The Go Playground.

That's all 😃.

Feel free to share if you found this useful 😃.


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