ng-if check if array is empty

The API I am working with returns this if there are no items in the array

items: []

If there are items in the array it returns something like

items: [
{
name: 'Bla'
}
]

In my template I believe I need to use ng-if to either show/hide an element based on whether there is data in there or not.

<p ng-if="post.capabilities.items"><strong>Topics</strong>: <span ng-repeat="topic in post.capabilities.items">{{topic.name}}</p>

However I could be totally off base as this is my first time working in Angular, and there may be a much better way to do what I am trying to do.

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最佳答案

post.capabilities.items will still be defined because it's an empty array, if you check post.capabilities.items.length it should work fine because 0 is falsy.

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Verify the length property of the array to be greater than 0:

<p ng-if="post.capabilities.items.length > 0">
<strong>Topics</strong>:
<span ng-repeat="topic in post.capabilities.items">
\{\{topic.name}}
</span>
</p>

Arrays (objects) in JavaScript are truthy values, so your initial verification <p ng-if="post.capabilities.items"> evaluates always to true, even if the array is empty.

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To overcome the null / undefined issue, try using the ? operator to check existence:

<p ng-if="post?.capabilities?.items?.length > 0">

  • Sidenote, if anyone got to this page looking for an Ionic Framework answer, ensure you use *ngIf:

    <p *ngIf="post?.capabilities?.items?.length > 0">
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In my experience, doing this on the HTML template proved difficult so I decided to use an event to call a function on TS and then check the condition. If true make condition equals to true and then use that variable on the ngIf on HTML

    emptyClause(array:any) {




if (array.length === 0) {
// array empty or does not exist


this.emptyMessage=false;


}else{


this.emptyMessage=true;
}
}

HTML

        <div class="row">


<form>
<div class="col-md-1 col-sm-1 col-xs-1"></div>
<div class="col-md-10 col-sm-10 col-xs-10">
<div [hidden]="emptyMessage" class="alert alert-danger">


No Clauses Have Been Identified For the Search Criteria


</div>
</div>
<div class="col-md-1 col-sm-1 col-xs-1"></div>
</form>


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