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

You can also use (focusout) event:

Use (eventName) for while binding event to DOM, basically () is used for event binding. Also you can use ngModel to get two way binding for your model. With the help of ngModel you can manipulate model variable value inside your component.

Do this in HTML file

<input type="text" [(ngModel)]="model" (focusout)="someMethodWithFocusOutEvent($event)">

And in your (component) .ts file

export class AppComponent { 
 model: any;
 constructor(){ }

 /*
 * This method will get called once we remove the focus from the above input box
 */
 someMethodWithFocusOutEvent() {
   console.log('Your method called');
   // Do something here
 }
}