I was in one of the angular presentation and one of the person in the meeting mentioned ng-bind
is better than {{}}
binding.
One of the reason, ng-bind
put the variable in the watch list and only when there is a model change the data get pushed to view, on the other hand, {{}}
will interpolate the expression every time (I guess it is the angular cycle) and push the value, even if the value changed or not.
Also it is said that, if you have not much data in on the screen you can use {{}}
and the performance issue will not be visible. Can someone shed some light on this issue for me?
In the first approach(i.e. {{}}), AngularJS evaluates the expression then replaces it with some value which sometime be left with the flashing double curly brackets but ng-bind saves this time by informing AngularJS to put the contents of the expression within the element itself.
The ng-bind directive tells AngularJS to replace the content of an HTML element with the value of a given variable, or expression. If the value of the given variable, or expression, changes, the content of the specified HTML element will be changed as well.
Two-way Binding Data binding in AngularJS is the synchronization between the model and the view. When data in the model changes, the view reflects the change, and when data in the view changes, the model is updated as well.
AngularJS creates a two way data-binding between the select element and the $ctrl.
Visibility:
While your angularjs is bootstrapping, the user might see your placed brackets in the html. This can be handled with ng-cloak
. But for me this is a workaround, that I don't need to use, if I use ng-bind
.
Performance:
The {{}}
is much slower.
This ng-bind
is a directive and will place a watcher on the passed variable. So the ng-bind
will only apply, when the passed value does actually change.
The brackets on the other hand will be dirty checked and refreshed in every $digest
, even if it's not necessary.
I am currently building a big single page app (~500 bindings per view). Changing from {{}} to strict ng-bind
did save us about 20% in every scope.$digest
.
Suggestion:
If you use a translation module such as angular-translate, always prefer directives before brackets annotation.
{{'WELCOME'|translate}}
=> <span ng-translate="WELCOME"></span>
If you need a filter function, better go for a directive, that actually just uses your custom filter. Documentation for $filter service
UPDATE 28.11.2014 (but maybe off the topic):
In Angular 1.3x the bindonce
functionality was introduced. Therefore you can bind the value of an expression/attribute once (will be bound when != 'undefined').
This is useful when you don't expect your binding to change.
Usage: Place ::
before your binding:
<ul> <li ng-repeat="item in ::items">{{item}}</li> </ul> <a-directive name="::item"> <span data-ng-bind="::value"></span>
Example:
ng-repeat
to output some data in the table, with multiple bindings per row. Translation-bindings, filter outputs, which get executed in every scope digest.
If you are not using ng-bind
, instead something like this:
<div> Hello, {{user.name}} </div>
you might see the actual Hello, {{user.name}}
for a second before user.name
is resolved (before the data is loaded)
You could do something like this
<div> Hello, <span ng-bind="user.name"></span> </div>
if that's an issue for you.
Another solution is to use ng-cloak
.
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