ngStyle: -

1)app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { HttpModule } from '@angular/http';
import { AppComponent } from './app.component';
@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

2)app.component.ts

import { Component } from '@angular/core';
import { FormsModule } from '@angular/forms';
@Component({
selector: 'app',
templateUrl: './app.component.html',
})
export class AppComponent{
    title: string = 'ngStyle Example' ;
    size: number = 12;
    color: string= 'red';
    styleClass: StyleClass = new StyleClass();
}

class StyleClass {
    color: string= 'blue';
    'font-size.%': number= 150;
    'font-weight': string= 'bold';
}

3)app.component.html

<p> {{title}} </p>
<div class='panel panel-primary'>
    <div class='panel-heading'>
        <p>Simple example of ngIf </p> 
    </div>
   <div class="panel-body">


        <input [(ngModel)]="color" />
        <div [ngStyle]="{'color': color}">
            Change my color
        </div>

        <input [(ngModel)]="size" />
       <div [ngStyle]="{'font-size.px': size}">
                Change my size
        </div>

       <div [ngStyle]="styleClass">
            Change my size & Color
        </div>

    </div>
</div>