I have a function in a separate JavaScript file that I would like to call in a React component - how can I achieve this?

I'm trying to create a slideshow, and in slideshow.js, I have this function that increases the current slide index, like so:

function plusSlides(n) {

    showSlides(slideIndex += n);

}

In Homepage.jsx, I have a next button that should call plusSlides from slideshow.js when it is clicked, like so:

class NextButton extends React.Component {

    constructor() {

        super();

        this.onClick = this.handleClick.bind(this);

    }



    handleClick (event) {

        script.plusSlides(1); // I don't know how to do this properly...

    }



    render() {

        return (

            <a className=next onClick={this.onClick}>

                &#10095;

            </a>

        );

    } 

}