default values

Node.js

function greet(name = 'stranger') {
  return `hello ${name}`
}
let message = greet()
console.log(message)
message = greet('bob')
console.log(message)

Output

hello stranger
hello bob

Go

use pointers and check for nil to know if explicitly left blank

package main
import "fmt"
func greet(name *string) string {
    n := "stranger"
    if name != nil {
        n = *name
    }
    return fmt.Sprintf("hello %s", n)
}
func main() {
    message := greet(nil)
    fmt.Println(message)
    name := "bob"
    message = greet(&name)
    fmt.Println(message)
}

Output

hello stranger
hello bob