Cloning part of state before update?

Question

React

By focus on the input, I try to clone this.state.collection and write it to oldCollection ,
after changing collection, it changes after oldCollection

//исходное состояние
        this.state = {
            collection: {item:true}
            oldCollection:null
        };

    onFocus() {//копирую по фокусу
        this.setState({
          oldCollection: this.state.collection
        });
    }

    itemChange(event) {//меняю исходный объект
        let collection = {item:false}
        this.setState({
            collection
        });
       console.log(this.state.oldCollection)//{item:false}
    }

why oldCollection changed the data next and how to fix it, Thanks!

Answer 1

this.setState({
 oldCollection: JSON.parse(JSON.stringify(collection))
});

Answer 2

How about oldCollection: {...this.state.collection}

Answer 3

Try looking in the direction of shouldComponentUpdate(nextProps, nextState). Also, in some cases, redux in one component is also suitable.