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bennadel/eval-async.htm

Created June 2, 2014 11:51
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Looking At How scope.$evalAsync() Affects Performance In AngularJS Directives
Raw
eval-async.htm
<!doctype html>
<html ng-app="Demo" ng-controller="AppController">
<head>
<meta charset="utf-8" />
<title>
Looking At How scope.$evalAsync() Affects Performance In AngularJS Directives
</title>
<link rel="stylesheet" type="text/css" href="./demo.css"></link>
</head>
<body>
<h1>
Looking At How scope.$evalAsync() Affects Performance In AngularJS Directives
</h1>
<h2>
Accessing DOM Layout Using scope.$evalSync()
&mdash;
<a ng-click="rebuild()">Rebuild</a>
</h2>
<div
ng-repeat="item in items"
bn-item
class="item">
ID: {{ item.id }}<br />
Coords: {{ x }} , {{ y }}<br />
</div>
<!-- Load scripts. -->
<script type="text/javascript" src="../../vendor/jquery/jquery-2.0.3.min.js"></script>
<script type="text/javascript" src="../../vendor/angularjs/angular-1.2.16.min.js"></script>
<script type="text/javascript">
// Create an application module for our demo.
var app = angular.module( "Demo", [] );
// -------------------------------------------------- //
// -------------------------------------------------- //
// I am the main application controller, providing data for the demo.
app.controller(
"AppController",
function( $scope ) {
// I hold the data being rendered in the ng-repeat.
$scope.items = buildItems( 1000 );
// ---
// PUBLIC METHODS.
// ---
// I rebuild the collection, forcing a re-rendering of the ng-repeat.
$scope.rebuild = function() {
$scope.items = buildItems( 1000 );
};
// ---
// PRIVATE METHODS.
// ---
// I return an item collection with given length.
function buildItems( count ) {
var items = new Array( count );
var now = ( new Date() ).getTime();
for ( var i = 0 ; i < count ; i++ ) {
items[ i ] = {
id: ( i + now )
};
}
return( items );
}
}
);
// -------------------------------------------------- //
// -------------------------------------------------- //
// I demonstrate how the directive link logic can affect performance.
app.directive(
"bnItem",
function() {
// I bind the JavaScript events to the local scope.
function link( $scope, element, attributes ) {
$scope.x = 0;
$scope.y = 0;
// By moving the DOM-query logic to an $evalAsync(), it will allow
// the ng-repeat loop to finish stamping out the cloned HTML nodes
// before the digest lifecycle goes back and starts to query for
// the DOM state in a later iteration. This gives the browser a
// chance to bulk-render the DOM.
$scope.$evalAsync(
function() {
var position = element.position();
$scope.x = Math.floor( position.left );
$scope.y = Math.floor( position.top );
}
);
}
// Return the directive configuration.
return({
link: link,
restrict: "A"
});
}
);
</script>
</body>
</html>
Raw
regular.htm
<!doctype html>
<html ng-app="Demo" ng-controller="AppController">
<head>
<meta charset="utf-8" />
<title>
Looking At How scope.$evalAsync() Affects Performance In AngularJS Directives
</title>
<link rel="stylesheet" type="text/css" href="./demo.css"></link>
</head>
<body>
<h1>
Looking At How scope.$evalAsync() Affects Performance In AngularJS Directives
</h1>
<h2>
Accessing DOM Layout During Linking
&mdash;
<a ng-click="rebuild()">Rebuild</a>
</h2>
<div
ng-repeat="item in items"
bn-item
class="item">
ID: {{ item.id }}<br />
Coords: {{ x }} , {{ y }}<br />
</div>
<!-- Load scripts. -->
<script type="text/javascript" src="../../vendor/jquery/jquery-2.0.3.min.js"></script>
<script type="text/javascript" src="../../vendor/angularjs/angular-1.2.16.min.js"></script>
<script type="text/javascript">
// Create an application module for our demo.
var app = angular.module( "Demo", [] );
// -------------------------------------------------- //
// -------------------------------------------------- //
// I am the main application controller, providing data for the demo.
app.controller(
"AppController",
function( $scope ) {
// I hold the data being rendered in the ng-repeat.
$scope.items = buildItems( 1000 );
// ---
// PUBLIC METHODS.
// ---
// I rebuild the collection, forcing a re-rendering of the ng-repeat.
$scope.rebuild = function() {
$scope.items = buildItems( 1000 );
};
// ---
// PRIVATE METHODS.
// ---
// I return an item collection with given length.
function buildItems( count ) {
var items = new Array( count );
var now = ( new Date() ).getTime();
for ( var i = 0 ; i < count ; i++ ) {
items[ i ] = {
id: ( i + now )
};
}
return( items );
}
}
);
// -------------------------------------------------- //
// -------------------------------------------------- //
// I demonstrate how the directive link logic can affect performance.
app.directive(
"bnItem",
function() {
// I bind the JavaScript events to the local scope.
function link( $scope, element, attributes ) {
// Using this approach, we are accessing the condition of the DOM
// while the ng-repeat loop is being rendered. This will force the
// browser to stop and repaint after each ng-repeat node is stamped-
// out so that it can apply the CSS and get the positioning.
var position = element.position();
$scope.x = Math.floor( position.left );
$scope.y = Math.floor( position.top );
}
// Return the directive configuration.
return({
link: link,
restrict: "A"
});
}
);
</script>
</body>
</html>
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