Set State for variables inside object

You should keep the non modified keys by using spread operator :

this.setState({
  ...this.state,
 person:{
 ...this.state.person,
 name:this.state.per_name,
 email:this.state.per_email
}
})

You can follow this practice for more clearance

constructor(props) {
    super(props)

    this.state = {
       per_name:'',
       per_email:'',
       person:{
           name:'',
           email:'',
           array:[]
        }
    }
}

someMethod() {
   const {person, per_name, per_email} = this.state;
   person.name = per_name;
   person.email = per_email;
   this.setState({
       person
   });
}