<h2>  {{'HOME.CONTENT' |  translate}}</h2>
 <button ion-button (click)="getLanguage()">lang</button>

getLanguage() {
    navigator.globalization.getPreferredLanguage(onSuccess, onError);
    function onSuccess(language) {
       alert('language: ' + language.value + 'n');
    }
    function onError(){
       alert('Error getting language');
    }
  }

navigator['globalization'].getPreferredLanguage(onSuccess, onError)