Although angular.element is very close to jQuery, it is still not possible to obtain elements directly through HTML tags. The simplest way is as follows:

angular.element(document.querySelector('p'));

http://jsfiddle.net/sy38y/2/

You can see it by looking at the document
The parameter requirement of angular.element() is HTML string or DOMElement, but what you write is a selector, which does not meet the parameter requirement of angular.element. If you want to use this usage, you need to add jquery

Change it to this:

    var par = document.getElementsByTagName('p')[0];
    angular.element(par).addClass('blue');

Angular does not recommend direct manipulation of the DOM, so if you want to add class, it is recommended to do so (I can't open your connection, I don't know how you wrote the code, so I will use my own)

HTML

<button ng-click="showActive()"></button>
<p ng-class="{'active':show===1}"></p>

js

$scope.showActive=function(){
    $scope.show=1;
}

angular.element(document).find('xx').addClass('yy')

Yes, I originally thought about passing the currently clicked button object through ng-click, but in the end I found that Angular does not allow this. . .
I had no choice but to use angular’s ​​built-in jQlite to handle it!