This property contains the name of a method that user-defined classes
may implement to hook into the up.util.copy() protocol.
Example
We have a user-defined Account class that we want to use with up.util.copy():
class Account {
constructor(email) {
this.email = email
}
[up.util.copy.key]() {
return new Account(this.email)
}
}
Note
The protocol method is not actually named 'up.util.copy.key'.
Instead it is named after the value of the up.util.copy.key property.
To do so, the code sample above is using a
computed property name
in square brackets.
We may now use Account instances with up.util.copy():
original = new User('foo[@foo](https://github.com/foo){: .is_secondary}.com')
copy = up.util.copy(original)
console.log(copy.email) // prints 'foo[@foo](https://github.com/foo){: .is_secondary}.com'
original.email = 'bar[@bar](https://github.com/bar){: .is_secondary}.com' // change the original
console.log(copy.email) // still prints 'foo[@foo](https://github.com/foo){: .is_secondary}.com'
