ngif not condition or condition code example

Example 1: ngif else

<div *ngIf="isLoggedIn; else loggedOut">
  Welcome back, friend.
</div>

<ng-template #loggedOut>
  Please friend, login.
</ng-template>

Example 2: angular conditional directives

//if 
<div *ngIf='[condition]'> </div>   
  //if [condition]==true the div will be shown

//for 
<div *ngFor='let [data] of [dataArray]; let i=index;'>
  <h2> {{i}} {{data.title}} </h2>
  <img src='{{data.image}}' />
  </div>   
  //the data contained in an array will be displayed element by element
  //similar to the function .map() in React

// ngStyle (conditional Style)
<div *ngFor='let [data] of [dataArray]; let i=index;'>
  <h2 [style.background]="i>1? 'green': 'red'"> {{i}} {{data.title}} </h2>

  </div> 

//if the index of the element is 1 or 0, the background will be red, if it is over 1 the background will be green