correct strategy to generate html dynamically with angular - angularjs

Question

I have a huge JSON object tree with two levels. First level has around 500 elements, and each element contains an average of 100 child elements.
I want to display the first level of the tree and I am doing it with a simple ng-repeat. When the user clicks on the element I want to display the child elements of that element. If I use a span ng-switch or a ng-show to show/hide child elements when the page first renders it freezes for around 10 seconds while generating all the HTML.
It doesn't sound like the right solution. There must be a different way of doing it, but I can't figure out. Anyone knows?

Answer 1

I have explained most in my comment, and here is a working plunker:
http://plunker.co/edit/RSZwfLlsCJ68MUkACbdp?p=preview
the new ng-if directive will do what you want
<h1>ng-if</h1> <h5>Click on the level to expand</h5>
<div class="well">
<ul class="nav nav-list" ng-repeat="(attr,element) in tree">
<li ng-click="expand=!expand" ng-class="{'active':expand}"><a>{{element.name}}</a></li>
<ul ng-if="expand" class="nav nav-list">
<li ng-repeat="item in element.items">{{item.name}}</li>
</ul>
</ul>
</div>
you can also do this in the "old-way" with ng-show using new ternary operator or its alternative expr && if_true || if_false
<h1>old-way</h1> <h5>Click on the level to expand</h5>
<small>use ternary operator or <pre>expand && element.items || []</pre></small>
<div class="well">
<ul class="nav nav-list" ng-repeat="(attr,element) in tree">
<li ng-click="expand=!expand" ng-class="{'active':expand}"><a>{{element.name}}</a></li>
<ul ng-show="expand" class="nav nav-list">
<li ng-repeat="item in (expand ? element.items : [])">{{item.name}}</li>
<!--<li ng-repeat="item in (expand && element.items || [])">{{item.name}}</li>-->
</ul>
</ul>
</div>

Answer 2

See this answer on ng-repeat performance. Essentially, it just takes a long time since Angular's ng-repeat, and basically all other directives, are set up to always look for updates in the whole JSON structure. So if you have lots of data and don't need live updates in the HTML view when changing the JSON, I wouldn't recommend using AngularJS. Generally, AngularJS performance also depends a lot on the browser and its JavaScript engine.
Alternatively, you could divide your JSON into subparts and then use pagination to display it.

Answer 3

I would recommend to fetch the data gradually from the server. Use server-side pagination and retrieve only the fields that you are going to display. Then, when a user clicks on one of the first level items, you can do another XHR to the server with the new data. I had similar requirements for a project and that solved the latency issue.
Regards,
Agustin.