How to use onBlur event on Angular2?

Use (eventName) while binding event to DOM, basically () is used for event binding. Also, use ngModel to get two-way binding for myModel variable.

Markup

<input type="text" [(ngModel)]="myModel" (blur)="onBlurMethod()">

Code

export class AppComponent { 
  myModel: any;
  constructor(){
    this.myModel="123";
  }
  onBlurMethod(){
   alert(this.myModel) 
  }
}

Demo

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Alternative 1

<input type="text" [ngModel]="myModel" (ngModelChange)="myModel=$event">

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Alternative 2 (not preferable)

<input type="text" #input (blur)="onBlurMethod($event.target.value)">

Demo

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For a model-driven form to fire validation on blur, you could pass updateOn parameter.

ctrl = new FormControl('', {
   updateOn: 'blur', //default will be change
   validators: [Validators.required]
}); 

Design Docs