Macro callback 

macro_rules! callback {
    (|| $body:expr) => { ... };
    (move || $body:expr) => { ... };
    (|$args:ident| $body:expr) => { ... };
    (move |$args:ident| $body:expr) => { ... };
    (|$args:ident : $args_type:ty | $body:expr) => { ... };
    (move |$args:ident : $args_type:ty| $body:expr) => { ... };
}

This macro is used to declare event for a Tag element using the ElementBuilder API

Example

Button.with_event(OnClick, callback!(move || log::info!("hello from js on click event")));