How to hide HTML template if a variable value is undedfined/null?

问题

I have used ngFor to display my data. And i want to hide a div if variable value from ngFor is empty/undefined. My code is below. Can anybody help.

<li *ngFor="let parcel of dataSource;">

   <span hidden="parcel.ID==''">{{parcel.refrence }}</span>
</li>

回答1:

Use *ngIf since your parcelID is undefined your condition should be *ngIf="parcel.ID"

<li *ngFor="let parcel of dataSource;">
   <span *ngIf="parcel.ID">{{parcel.refrence }}</span>
</li>

回答2:

use this code -

<li *ngFor="let parcel of dataSource;">
   <span [hidden]="parcel.ID !== ''">{{parcel.refrence }}</span>
</li>

or

<li *ngFor="let parcel of dataSource;">
   <span *ngIf="parcel.ID == ''">{{parcel.refrence }}</span>
</li>

the syntax for hidden is [hidden]

来源：https://stackoverflow.com/questions/42971883/how-to-hide-html-template-if-a-variable-value-is-undedfined-null