jellyfin-web/src/scripts/settings/webSettings.js

let data;

async function getConfig() {
    if (data) return Promise.resolve(data);
    try {
        const response = await fetch('config.json', {
            cache: 'no-cache'
        });

        if (!response.ok) {
            throw new Error('network response was not ok');
        }

        data = await response.json();

        return data;
    } catch (error) {
        console.warn('failed to fetch the web config file:', error);
        return getDefaultConfig();
    }
}

async function getDefaultConfig() {
    try {
        const response = await fetch('config.template.json', {
            cache: 'no-cache'
        });

        if (!response.ok) {
            throw new Error('network response was not ok');
        }

        data = await response.json();
        return data;
    } catch (error) {
        console.error('failed to fetch the default web config file:', error);
    }
}

export function getMultiServer() {
    return getConfig().then(config => {
        return config.multiserver;
    }).catch(error => {
        console.log('cannot get web config:', error);
        return false;
    });
}

export function getThemes() {
    return getConfig().then(config => {
        return config.themes;
    }).catch(error => {
        console.log('cannot get web config:', error);
        return [];
    });
}

export function getPlugins() {
    return getConfig().then(config => {
        return config.plugins;
    }).catch(error => {
        console.log('cannot get web config:', error);
        return [];
    });
}