typescript - Angular 2 Show and Hide an element

Question

I'm having a problem hiding and showing an element depending of a boolean variable in Angular 2.

this is the code for the div to show and hide:

<div *ngIf="edited==true" class="alert alert-success alert-dismissible fade in" role="alert">
        <strong>List Saved!</strong> Your changes has been saved.
</div>

the variable is "edited" and it's stored in my component:

export class AppComponent implements OnInit{

  (...)
  public edited = false;
  (...)
  saveTodos(): void {
   //show box msg
   this.edited = true;
   //wait 3 Seconds and hide
   setTimeout(function() {
       this.edited = false;
       console.log(this.edited);
   }, 3000);
  }
}

The element is hidden, when saveTodos function starts, the element is shown, but after 3 seconds, even if the variable come back to be false, the element does not hide. Why?

Answer 1

There are two options depending what you want to achieve :

1. You can use the hidden directive to show or hide an element

   <div [hidden]="!edited" class="alert alert-success box-msg" role="alert">
     <strong>List Saved!</strong> Your changes has been saved.
   </div>
   

2. You can use the ngIf control directive to add or remove the element. This is different of the hidden directive because it does not show / hide the element, but it add / remove from the DOM. You can loose unsaved data of the element. It can be the better choice for an edit component that is cancelled.

   <div *ngIf="edited" class="alert alert-success box-msg" role="alert"> 
     <strong>List Saved!</strong> Your changes has been saved.
   </div>
   

For you problem of change after 3 seconds, it can be due to incompatibility with setTimeout. Did you include angular2-polyfills.js library in your page ?