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Go from TS

null & undefined

Go doesn’t have null or undefined like JavaScript. To support use cases where you need to represent the absence of a value, Go uses nil.

As we’ve just learned, uninitialized variables in Go are set to their zero value, so only specific types can be nil. Basic types like int, float, and string cannot be nil. However, pointers, slices, maps, channels, interfaces, and function types can be nil.

Signaling optionality

Section titled “Signaling optionality”

As mentioned in the function arguments section, Go doesn’t support optional arguments. A common pattern to signal optionality is to use a pointer type. This way you can pass nil to indicate that the argument is not provided.

optional.go
package main
import "fmt"


func greet(name *string) {
    if name == nil {
        fmt.Println("Hello Unknown User!")
    } else {
        fmt.Printf("Hello, %s!\n", *name)
    }
}


func main() {
    var name *string // Set to nil due to zero value
    greet(name) // Output: Hello Unknown User!


    nameValue := "John"
    name = &nameValue
    greet(name) // Output: Hello, John!
}

Note the * before string in the greet function signature. This indicates that name is a pointer to a string.

We’ll discuss pointer in more detail later as they are a new and very important concept in Go. For the meantime just know that with pointers you can indicate that a variable is optional. In the example above we could also pass nil directly:

optional.go
func main() {
    greet(nil) // Output: Hello Unknown User!
}

However it’s not possible to omit the argument completely. You still need to pass nil explicitly!