🔀 Reactive Branching: $if( )

The $if function is a reactive control flow operator. It manages the conditional rendering of components, ensuring that only the active branch exists in the DOM and in memory.

🛠️ Function Signature

$if(
  condition: Signal<boolean> | Function, 
  thenVal: Component | Node, 
  otherwiseVal?: Component | Node
): HTMLElement

Parameter	Type	Required	Description
condition	Signal	Yes	A reactive source that determines which branch to render.
thenVal	any	Yes	The content to show when the condition is truthy.
otherwiseVal	any	No	The content to show when the condition is falsy (defaults to null).

Returns: A div element with display: contents that acts as a reactive portal for the branches.

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📖 Usage Patterns

1. Simple Toggle

The most common use case is showing or hiding a single element based on a state.

const isVisible = $(false);

Div([
  Button({ onclick: () => isVisible(!isVisible()) }, "Toggle Message"),
  
  $if(isVisible, 
    P("Now you see me!"), 
    P("Now you don't...")
  )
]);

2. Lazy Component Loading

Unlike using a hidden class (CSS display: none), $if is lazy. The branch that isn't active is never created. This saves memory and initial processing time.

$if(() => user.isLogged(), 
  () => Dashboard(), // Only executed if logged in
  () => LoginGate()  // Only executed if guest
)

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🧹 Automatic Cleanup

One of the core strengths of $if is its integrated Cleanup logic. SigPro ensures that when a branch is swapped out, it is completely purged.

1. Stop Watchers: All $.watch calls inside the inactive branch are permanently stopped.
2. Unbind Events: Event listeners attached via $.html are removed.
3. Recursive Sweep: SigPro performs a deep "sweep" of the removed branch to ensure no nested reactive effects remain active.

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💡 Best Practices

• Function Wrappers: If your branches are heavy (e.g., they contain complex components), wrap them in a function () => MyComponent(). This prevents the component from being initialized until the condition actually meets its requirement.
• Logical Expressions: You can pass a complex computed function as the condition:

  $if(() => count() > 10 && status() === 'ready', 
    Span("Threshold reached!")
  )

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🏗️ Technical Comparison

Feature	Standard CSS hidden	SigPro $if
DOM Presence	Always present	Only if active
Reactivity	Still processing in background	Paused/Destroyed
Memory usage	Higher	Optimized
Cleanup	Manual	Automatic