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https://github.com/Pasvaz/bindonce

Zero watches binding for AngularJs
https://github.com/Pasvaz/bindonce

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Zero watches binding for AngularJs

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Bindonce

========



High performance binding for AngularJs



## Usage

* download, clone or fork it or install it using [bower](http://twitter.github.com/bower/) `bower install angular-bindonce`

* Include the `bindonce.js` script provided by this component into your app.

* Add `'pasvaz.bindonce'` as a module dependency to your app: `angular.module('app', ['pasvaz.bindonce'])`



## Demo

Here is an example of how AngularJs can [freeze your UI](http://plnkr.co/edit/jwrHVb?p=preview), try to press and hold a key inside the input field, when the table is filled with only 1 person everything is ok, you can see how the DOM is updated by the input in real time, however if you try to load 1000 person *(or even 500 if the testing device is not powerfull)* and repeat the experiment you can see how the UI is frozen. In [this other demo](http://plnkr.co/edit/0DGOrk?p=preview) BindOnce will take care of your watchers and the UI will be reactive as it should be. The code is the same for both demos, the only difference is that I replaced any `ng-*` tag inside the table with the equivalent `bo-*` tag.

* [AngularJs regular Demo](http://plnkr.co/edit/jwrHVb?p=preview)

* [Demo with Bindonce](http://plnkr.co/edit/0DGOrk?p=preview)



## Overview

AngularJs provides a great data binding system but if you abuse of it the page can run into some performance issues, it's known that more of 2000 watchers can lag the UI and that amount can be reached easily if you don't pay attention to the data-binding. Sometime you really need to bind your data using watchers, especially for SPA because the data are updated in real time, but often you can avoid it with some efforts, most of the data presented in your page, once rendered, are immutable so you shouldn't keep watching them for changes.



For instance, take a look to this snippet:

```html

    

    	
  • 

    		

    		

    		
    

    	
    • 



```

Angular internally creates a `$watch` for each `ng-*` directive in order to keep the data up to date, so in this example just for displaying few info it creates 6 + 1 *(ngRepeatWatch)* watchers per `person`, even if the `person` is supposed to remain the same once shown. Iterate this amount for each person and you can have an idea about how easy is to reach 2000 watchers. Now if you need it because those data could change while you show the page or are bound to some models, it's ok. But most of the time they are static data that don't change once rendered. This is where **bindonce** can really help you.



The above example done with **bindonce**:

```html

    

    	
  • 

    		

    		

    		
    

    	
    • 



```

Now this example uses **0 watches** per `person` and renders exactly the same result as the above that uses ng-*. *(Angular still uses 1 watcher for ngRepeatWatch)*



### The smart approach

OK until here nothing completely new, with a bit of efforts you could create your own directive and render the `person` inside the `link` function, or you could use [watch fighters](https://github.com/abourget/abourget-angular) that has a similar approach, but there is still one problem that you have to face and **bindonce** already handles it: *the existence of the data when the directive renders the content*. Usually the directives, unless you use watchers or bind their attributes to the scope (still a watcher), render the content when they are loaded into the markup, but if at that given time your data is not available, the directive can't render it. Bindonce can wait until the data is ready before to rendering the content.

Let's take a look at the follow snippet to better understand the concept:

```html





...



angular.module('testApp', [])

.directive('myCustomSetText', function () {

	return {

		link:function (scope, elem, attr, ctrl) {

			elem.text(scope.$eval(attr.myCustomSetText));

		}

	}

});



```

This basic directive works as expected, it renders the `Person` data without using any watchers. However, if `Person` is not yet available inside the $scope when the page is loaded (say we get `Person` via $http or via $resource), the directive is useless, `scope.$eval(attr.myCustomSetText)` simply renders nothing and exits.



Here is how we can solve this issue with **bindonce**:

```html



	

	

	

	




```

`bindonce="Person"` does the trick, any `bo-*` attribute belonging to `bindonce` waits until the parent `bindonce="{somedata}"` is validated and then renders its content. Once the scope contains the value `Person` then each bo-* child gets filled with the proper values. In order to accomplish this task, **bindonce** uses just **one** temporary watcher, no matters how many children need to be rendered. As soon as it gets `Person` the watcher is promptly removed. If the $scope already contains the data `bindonce` is looking for, then it doesn't create the temporary watcher and simply starts rendering its children.



You may have noticed that the first example didn't assign any value to the `bindonce` attribute:

```html

    

    	
  • 

    	...

    ```

    when used with `ng-repeat` `bindonce` doesn't need to check if `person` is defined because `ng-repeat` creates the directives only when `person` exists. You could be more explicit: `
    • 

  • `, however assigning a value to `bindonce` in an `ng-repeat` won't make any difference.
    


    ### Interpolation

    Some directives (ng-href, ng-src) use interpolation, ie: `ng-href="/profile/{{User.profileId}}"`.

    Both `ng-href` and `ng-src` have the bo-* equivalent directives: `bo-href-i` and `bo-src-i` (pay attention to the **-i**, it stands for **interpolate**). As expected they don't use watchers however Angular creates one watcher per  interpolation, for instance `bo-href-i="/profile/{{User.profileId}}"` sets the element's href **once**, as expected, but Angular keeps a watcher active on `{{User.profileId}}` even if `bo-href-i` doesn't use it.

    That's why by default the `bo-href` doesn't use interpolation or watchers. The above equivalent with 0 watchers would be `bo-href="'/profile/' + User.profileId"`. Nevertheless, `bo-href-i` and `bo-src-i` are still maintained for compatibility reasons.
    


    ### Filters

    Almost every `bo-*` directive replace the equivalent `ng-*` and works in the same ways, except it is evaluated once. 

    Consequentially you can use any valid angular expression, including filters. This is an example how to use a filter:

    ```html

    

    	

    

    ```
    


    ## Attribute Usage

    | Directive  | 	Description | 	Example  |

    |------------|----------------|-----|

    | `bindonce="{somedata}"`| **bindonce** is the main directive. `{somedata}` is optional, and if present, forces bindonce to wait until `somedata` is defined before rendering its children  | `
    ...
    ` |

    | `bo-if = "condition"`     | equivalent to `ng-if` but doesn't use watchers |``|

    | `bo-switch = "expression"`     | equivalent to `ng-switch` but doesn't use watchers |`
    ` `public` `private` `
    `|

    | `bo-show = "condition"`     | equivalent to `ng-show` but doesn't use watchers |``|

    | `bo-hide = "condition"`     | equivalent to `ng-hide` but doesn't use watchers |``|

    | `bo-disabled = "condition"`     | equivalent to `ng-disabled` but doesn't use watchers |``|

    | `bo-text = "text"`      | evaluates "text" and print it as text inside the element | `` |

    | `bo-bind = "text"`      | alias for `bo-text`, equivalent to `ng-bind` but doesn't use watchers | `` |

    | `bo-html = "markup"`      | evaluates "markup" and render it as html inside the element |`bo-html="Person.description"`|

    | `bo-href-i = "url"`
    *use `bo-href` instead* | **equivalent** to `ng-href`.
    **Heads up!** Using interpolation `{{}}` it creates one watcher: 
    `bo-href-i="/p/{{Person.id}}"`. 
    Use `bo-href` to avoid the watcher:
     `bo-href="'/p/' + Person.id"` |``|

    | `bo-href = "url"`      | **similar** to `ng-href` but doesn't allow interpolation using `{{}}` like `ng-href`. 
    **Heads up!** You can't use interpolation `{{}}` inside the url, use bo-href-i for that purpose |`` 
    or
     ``|

    | `bo-src-i = "url"`
    *use `bo-src` instead* | **equivalent** to `ng-src`. 
    **Heads up!** It creates one watcher |``|

    | `bo-src = "url"`      | **similar** to `ng-src` but doesn't allow interpolation using `{{}}` like `ng-src`. 
    **Heads up!** You can't use interpolation `{{}}`, use bo-src-i for that purpose |``|

    | `bo-class = "object/string"`      | equivalent to `ng-class` but doesn't use watchers |``|

    | `bo-alt = "text"`      | evaluates "text" and render it as `alt` for the element |``|

    | `bo-title = "text"`      | evaluates "text" and render it as `title` for the element |``|

    | `bo-id = "#id"`      | evaluates "#id" and render it as `id` for the element |``|

    | `bo-style = "object"`      | equivalent to `ng-style` but doesn't use watchers |``|

    | `bo-value = "expression"`      | evaluates "expression" and render it as `value` for the element |``|

    | `bo-attr bo-attr-foo = "text"`      | evaluates "text" and render it as a custom attribute for the element |`
    `|
    


    ## Build

    ```

    $ npm install uglify-js -g

    $ uglifyjs bindonce.js -c -m -o bindonce.min.js

    ```
    


    ## Todo

    Tests
    


    ## Copyright

    BindOnce was written by **Pasquale Vazzana**, you can follow him on [google+](https://plus.google.com/101872882413388363602) or on [@twitter](https://twitter.com/PasqualeVazzana)
    


    Thanks to all the [contributors](https://github.com/Pasvaz/bindonce/graphs/contributors)
    


    ## LICENSE - "MIT License"
    


    Copyright (c) 2013-2014 Pasquale Vazzana
    


    Permission is hereby granted, free of charge, to any person obtaining a copy

    of this software and associated documentation files (the "Software"), to deal

    in the Software without restriction, including without limitation the rights

    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

    copies of the Software, and to permit persons to whom the Software is

    furnished to do so, subject to the following conditions:
    


    The above copyright notice and this permission notice shall be included in

    all copies or substantial portions of the Software.
    


    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

    THE SOFTWARE.

    

    

    

    •