Macro watch 

watch!() { /* proc-macro */ }

The watch! macro for creating reactive side effects.

Watches one or more signals and executes a closure whenever any of them changes. The closure is also executed once immediately with the current signal values during initialisation. This initial execution is wrapped in a suppressed-update scope so that any .set() calls inside the body do not trigger unnecessary DynamicNode re-renders.

The number of signal expressions must match the number of closure parameters. Each closure parameter receives the current value (via .get()) of the corresponding signal.

let count = use_signal(|| 0_i32);
let name = use_signal(|| String::from("euv"));
watch!(count, name, |count_val, name_val| {
    web_sys::console::log_1(&format!("count={}, name={}", count_val, name_val).into());
});