AngularJS : Why ng-bind is better than {{}} in angular?

AngularJS : Why ng-bind is better than {{}} in angular?

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?

Solutions/Answers:

Solution 1:

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.

Solution 2:

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.

Solution 3:

ng-bind is better than {{...}}

For example, you could do:

<div>
  Hello, {{variable}}
</div>

This means that the whole text Hello, {{variable}} enclosed by <div> will be copied and stored in memory.

If instead you do something like this:

<div>
  Hello, <span ng-bind="variable"></span>
</div>

Only the value of the value will be stored in memory, and angular will register a watcher (watch expression) which consists of the variable only.

Solution 4:

Basically the double-curly syntax is more naturally readable and requires less typing.

Both cases produce the same output but.. if you choose to go with {{}} there is a chance that the user will see for some milliseconds the {{}} before your template is rendered by angular. So if you notice any {{}} then is better to use ng-bind.

Also very important is that only in your index.html of your angular app you can have un-rendered {{}}. If you are using directives so then templates, there is no chance to see that because angular first render the template and after append it to the DOM.

Solution 5:

{{...}} is meant two-way data binding. But, ng-bind is actually meant for one-way data binding.

Using ng-bind will reduce the number of watchers in your page. Hence ng-bind will be faster than {{...}}. So, if you only want to display a value and its updates, and do not want to reflect its change from UI back to the controller, then go for ng-bind. This will increase the page performance and reduce the page load time.

<div>
  Hello, <span ng-bind="variable"></span>
</div>

Solution 6:

This is because with {{}} the angular compiler considers both the text node and it’s parent as there is a possibility of merging of 2 {{}} nodes. Hence there are additional linkers that add to the load time. Of course for a few such occurrences the difference is immaterial, however when you are using this inside a repeater of large number of items, it will cause an impact in slower runtime environment.