title: Angular2 control validation when a user finishes typing
body: <p>I would like to perform validation with tthe server to check if an email is already registered but only on blur not on value change </p>
  
  <p>I have an option to add multiple controls and this is how ive organized my form</p>
  
  <pre><code>    ngOninit(){
        this.userForm = this._formBuilder.group({
         others: this._formBuilder.array([])  //multiple
        });
  
        this.onAddControl();  //allows adding multiple items
      }
  
  
  
      onAddControl(){
  
          return this._formBuilder.group({
           email: ['' [this._validateServ.emailDoesntExistsValidator.bind(this._validateServ)]
           ],
  
         });
     }
   }
  </code></pre>
  
  <p>Now on the <code>_validateServ</code></p>
  
  <pre><code>emailDoesntExistsValidator(control) {
    if (control.value != undefined) {
      if(!this.emailValueValidator(control)){
         return this._authService.checkExists("email",control.value)  //http request
          .map(response =&gt; {
            if (response) {
              return {'emailTaken': true};
           }
        });
      }
  
    }
  }
  </code></pre>
  
  <p>I would like the email validation to run on blur since it is performing a http request so that i can show the waiting as http request is being performed
  The above works but works on each keypress but not on blur event</p>