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# Links System
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Advanced reactive programming system for creating property links between Panel components and Bokeh models. Enables sophisticated reactive patterns and cross-component data synchronization without Python callback overhead.
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## Capabilities
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### Property Linking
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Core classes for establishing reactive links between component properties.
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```python { .api }
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class Link:
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    """
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    Base class for linking properties between components.
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    Parameters:
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    - source: Source component with properties to link from
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    - target: Target component with properties to link to
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    - properties: Dictionary mapping source properties to target properties
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    - bidirectional: Whether link should work in both directions
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    """
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class Callback:
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    """
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    Base callback class for reactive programming patterns.
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    Parameters:
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    - source: Source component to watch for changes
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    - target: Target component to update
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    - code: JavaScript or Python code to execute on changes
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    """
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```
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### JavaScript Links
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High-performance client-side property linking using JavaScript callbacks.
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```python { .api }
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class JSCallbackGenerator:
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    """Generates JavaScript callbacks for client-side property linking"""
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class JSLinkCallbackGenerator:
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    """Specialized generator for JavaScript property links between components"""
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```
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## Usage Examples
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### Basic Property Linking
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```python
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import panel as pn
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# Create components
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slider = pn.widgets.IntSlider(start=0, end=100, value=50)
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number_input = pn.widgets.NumberInput(value=50)
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# Link slider value to number input
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pn.links.Link(slider, number_input, properties={'value': 'value'})
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# Bidirectional linking
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pn.links.Link(slider, number_input, properties={'value': 'value'}, bidirectional=True)
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```
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### JavaScript Links for Performance
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```python
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import panel as pn
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# High-performance client-side linking
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text_input = pn.widgets.TextInput(value="Hello")
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markdown = pn.pane.Markdown("Hello")
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# JavaScript link for immediate updates without server roundtrip
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pn.links.JSLink(text_input, markdown, properties={'value': 'object'})
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```
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The links system is essential for building responsive applications with complex component interactions and is particularly valuable for performance-critical applications where minimizing server roundtrips is important.