NewComponent.js

const React = require('react');

class NewComponent extends React.Component {
    constructor(props) {
        super(props);
        this.onMouseOver = this.onMouseOver.bind(this);
    }
    onMouseOver() {
        this.props.onMouseOver(this.props.id);
    }
    render() {
        return (
            <div onMouseOver={this.onMouseOver} onMouseLeave={this.props.onMouseLeave}>
                { props.isHovering ? 'I am being hovered over' : '' }
            </div>
        )
    }
}

export default NewComponent

NewContainer.js

const items = [
    { id: 1, name: 'ABC' },
    { id: 2, name: 'EFG' },
    { id: 3, name: 'HIJ' },
]

class NewContainer extends Component {
    contructor(props) {
        super(props)

        this.state = {
            hoverID: null
        }
    }
    handleMouseOver = (id) => {
        this.setState({
            hoverID: id
        })
    }
    handleMouseLeave = () => {
        this.setState({
            hoverID: null
        })
    }
    render() {
        const { hoverID } = this.state

        return (
            { items.map(item => 
                <NewComponent
                    id={item.id}
                    onMouseOver={this.handleMouseOver}
                    onMouseLeave={this.handleMouseLeave}
                    isHover={hoverID === item.id} />
            ) }
        )
    }
}