Determining if an array is devoid of any elements using ng-if

When the API I am dealing with has no items in the array, it returns:

items: []

If there are elements in the array, it looks something like this:

items: [
  {
    name: 'Bla'
  }
]

I suspect that in my template, I will need to utilize ng-if to display or hide an element based on whether there is any data present.

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

However, since this is my first time working with Angular, I may not be entirely accurate, and there might be a more efficient way to achieve what I have in mind.

javascriptarraysangularjs

Answer №1

post.capabilities.items remains intact as an empty array; by verifying post.capabilities.items.length, it should function properly since 0 is considered falsy.

Answer №2

Ensure that the length property of the array is 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>

In JavaScript, arrays (objects) are considered truthy values, so even if the array is empty, the initial verification 

<p ng-if="post.capabilities.items">
will always evaluate to true.

Answer №3

To tackle the problem of null or undefined, consider utilizing the ? operator to verify existence:

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

  • On a side note, if you landed on this page seeking an Ionic Framework solution, make sure to use *ngIf:

    <p *ngIf="post?.capabilities?.items?.length > 0">

Answer №4

here is the solution:

 <div *ngIf="post.capabilities.items.length > 0 && post.capabilities.items[0] !== '' "> ..... </div>

This code snippet checks whether there are any items in post.capabilities.items and also ensures that the first item is not an empty string before displaying content. It makes sure that content is only shown when there are items available in post.capabilities.items and the first item is not an empty string.

Answer №5

After encountering some challenges trying to implement this directly on the HTML template, I opted to utilize an event to trigger a function in TypeScript that would then evaluate the condition. If the condition is true, I set a variable to true and then used that variable in the ngIf statement in the 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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