loader.js

// Load maxResults setting
chrome.storage.local.get(['maxresults'], function (result) {
    // Check if loading successful, else use fallback
    let maxResults = 5;
    if (result.maxresults) {
        maxResults = parseInt(result.maxresults);
    }

    // Inject maxResults + localisation into main.js
    let newItemsTitle = chrome.i18n.getMessage("newItemsTitle");
    let oldItemsTitle = chrome.i18n.getMessage("oldItemsTitle");
    let actualCode = `let maxResults = ${maxResults}; let newItemsTitle = "${newItemsTitle}"; let oldItemsTitle = "${oldItemsTitle}";`;
    let script = document.createElement('script');
    script.textContent = actualCode;
    (document.head || document.documentElement).appendChild(script);
    script.remove();

    // Inject main.js into YouTube page
    // This is required to interact with YouTube's Polymere and display video suggestions nicely
    script = document.createElement('script');
    script.src = chrome.extension.getURL('main.js');
    (document.head || document.documentElement).appendChild(script);
    script.remove();
});