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AngularJS: A More Effective Method for Height Change Monitoring
In the case of variable height navigation, where a rigidly positioned navigation bar resides atop content with a margin-top derived from the navigation height, asynchronous data loading can lead to changes in the navigation height, requiring adjustment of the content margin.
Previously, a timer-based approach was employed to address this issue. However, this approach introduced potential drawbacks related to aesthetics and latency. Is there a more effective way to monitor height changes in AngularJS?
Yes, there is. By utilizing the watch capability in AngularJS, a solution can be devised that offers enhanced responsiveness and eliminates the need for timers. This works by registering a watch in the emHeightSource directive that is triggered with each $digest cycle.
Within the watch, the __height property is updated. This property is then monitored by another watch in the emHeightTarget directive. When the __height property changes, the margin-top of the target element is adjusted accordingly.
The improved implementation using watch:
/* * Get notified when height changes and change margin-top */ .directive( 'emHeightTarget', function() { return { link: function( scope, elem, attrs ) { scope.$watch( '__height', function( newHeight, oldHeight ) { elem.attr( 'style', 'margin-top: ' + (58 + newHeight) + 'px' ); } ); } } } ) /* * Checks every $digest for height changes */ .directive( 'emHeightSource', function() { return { link: function( scope, elem, attrs ) { scope.$watch( function() { scope.__height = elem.height(); } ); } } } )
This approach provides a self-contained solution that addresses the shortcomings of the timer-based method, ensuring responsive and seamless height change detection and margin adjustment.
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