How can I write data attributes using Angular?

About access

<ol class="viewer-nav">
    <li *ngFor="let section of sections" 
        [attr.data-sectionvalue]="section.value"
        (click)="get_data($event)">
        {{ section.text }}
    </li>  
</ol>

And

get_data(event) {
   console.log(event.target.dataset.sectionvalue)
}

Use attribute binding syntax instead

<ol class="viewer-nav"><li *ngFor="let section of sections" 
    [attr.data-sectionvalue]="section.value">{{ section.text }}</li>  
</ol>

or

<ol class="viewer-nav"><li *ngFor="let section of sections" 
    attr.data-sectionvalue="{{section.value}}">{{ section.text }}</li>  
</ol>

See also :

• How to add conditional attribute in Angular 2?