问题
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?
回答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.
回答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.
回答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.
回答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.
回答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>
回答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.
回答7:
The reason why Ng-Bind is better because,
When Your page is not Loaded or when your internet is slow or when your website loaded half, then you can see these type of issues (Check the Screen Shot with Read mark) will be triggered on Screen which is Completly weird. To avoid such we should use Ng-bind
回答8:
ng-bind has its problems too.When you try to use angular filters, limit or something else, you maybe can have problem if you use ng-bind. But in other case, ng-bind is better in UX side.when user opens a page, he/she will see (10ms-100ms) that print symbols ( {{ ... }} ), that's why ng-bind is better.
回答9:
There is some flickering problem in {{ }} like when you refresh the page then for a short spam of time expression is seen.So we should use ng-bind instead of expression for data depiction.
回答10:
ng-bind is also safer because it represents html as a string.
So for example, '<script on*=maliciousCode()></script>' will be displayed as a string and not be executed.
回答11:
According to Angular Doc:
Since ngBind is an element attribute, it makes the bindings invisible to the user while the page is loading... it's the main difference...
Basically until every dom elements not loaded, we can not see them and because ngBind is attribute on the element, it waits until the doms come into play... more info below
ngBind
- directive in module ng
The ngBind attribute tells AngularJS to replace the text content of the specified HTML element with the value of a given expression, and to update the text content when the value of that expression changes.
Typically, you don't use ngBind directly, but instead you use the double curly markup like {{ expression }} which is similar but less verbose.
It is preferable to use ngBind instead of {{ expression }} if a template is momentarily displayed by the browser in its raw state before AngularJS compiles it. Since ngBind is an element attribute, it makes the bindings invisible to the user while the page is loading.
An alternative solution to this problem would be using the ngCloak directive. visit here
for more info about the ngbind visit this page: https://docs.angularjs.org/api/ng/directive/ngBind
You could do something like this as attribute, ng-bind:
<div ng-bind="my.name"></div>
or do interpolation as below:
<div>{{my.name}}</div>
or this way with ng-cloak attributes in AngularJs:
<div id="my-name" ng-cloak>{{my.name}}</div>
ng-cloak avoid flashing on the dom and wait until all be ready! this is equal to ng-bind attribute...
回答12:
You can refer to this site it will give you a explanation which one is better as i know {{}} this is slower than ng-bind.
http://corpus.hubwiz.com/2/angularjs/16125872.html refer this site.
来源：https://stackoverflow.com/questions/16125872/angularjs-why-ng-bind-is-better-than-in-angular