Class & style helpers

[class], [class.foo], [style], [style.width.%], [ngClass], [ngStyle]

With binding

<span [class]="tag.slug">{{tag.name}}</span> - overwrites the whole class
<span [class.popular]="tag.count > 100">{{tag.name}}</span> - set className
<button [style.font-size.em]="isSpecial ? 2 : 1.2">...</button> - set one style element with unit

With builtin directives

classes = { selected: this.selected, promo: this.promo };
styles = { 'font-size': this.selected ? '1.2em' : '1em' };

In the html:

[ngClass]="classes"
[ngStyle]="styles"