bookstack/resources/js/components/details-highlighter.js

class DetailsHighlighter {

    constructor(elem) {
        this.elem = elem;
        this.dealtWith = false;
        elem.addEventListener('toggle', this.onToggle.bind(this));
    }

    onToggle() {
        if (this.dealtWith) return;

        if (this.elem.querySelector('pre')) {
            window.importVersioned('code').then(Code => {
                Code.highlightWithin(this.elem);
            });
        }
        this.dealtWith = true;
    }
}

export default DetailsHighlighter;