import { LightningElement,track } from 'lwc';

export default class TrackDemo extends LightningElement {

    @track fullName={firstName:"",lastName:""};

    handleChange(event){
        const field=event.target.name;
       // window.alert(field)

        if(field === 'firstName'){
            this.fullName.firstName=event.target.value;
        }
        else if(field === 'lastName'){
            this.fullName.lastName=event.target.value;
        }

    }
}