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