Chrome skladovanie sync vstupná hodnota

Snažím sa dostať vstupná hodnota v mojom main.js (obsah skriptu), ale bojujem, aby finialize to nejako. Som maged ak chcete uložiť hodnotu s windows.onload prístup ako môžete vidieť nižšie v mojom popup.js. Ale nemôžem si to za obsah skriptu. Chcem použiť hodnotu ako premenná "userInput" v mojom obsah skriptu.

popup.js:

function registerButtonAction(tabId, button, action) {
    // clicking button will send a message to
    // content script in the same tab as the popup
    button.addEventListener('click', () => chrome.tabs.sendMessage(tabId, { [action]: true }));
}

function setupButtons(tabId) {
    // add click actions to each 3 buttons
    registerButtonAction(tabId, document.getElementById('start-btn'), 'startSearch');
    registerButtonAction(tabId, document.getElementById('deals-btn'), 'startDeals');
    registerButtonAction(tabId, document.getElementById('stop-btn'), 'stopSearch');
}

function injectStartSearchScript() {
    chrome.tabs.query({ active: true, currentWindow: true }, function (tabs) {
        // Injects JavaScript code into a page
        // chrome.tabs.executeScript(tabs[0].id, { file: 'main.js' });

        // add click handlers for buttons
        setupButtons(tabs[0].id);
    });
}

injectStartSearchScript();

window.onload = function () {
    document.getElementById('save-btn').onclick = function () {
        let valueInput = document.getElementById('deal-ipt').value;

        chrome.storage.sync.set({ 'maxBidDeal': valueInput }, function () {
            alert('Saved!');
        });
    };
};

zoznam lodného nákladu.json:

{
    "manifest_version": 2,
    "name": "test app",
    "description": "test desc",
    "version": "1.0",
    "browser_action": {
        "default_icon": "icon.png",
        "default_popup": "popup.html"
    },
    "permissions": ["tabs", "<all_urls>", "storage"],
    "content_scripts": [
        {
            "matches": ["<all_urls>"],
            "js": ["main.js"]
        }
    ],
    "content_security_policy": "script-src 'self' https://ajax.googleapis.com; object-src 'self'"
}

main.js:

function startSearch() {
// does soemthing
}

function deals() {
// here is my variable userInput
userInput = 
}

chrome.runtime.onMessage.addListener((message) => {
    // choose action based on received message:
    if (message.startSearch) {
        startSearch();
    } else if (message.startDeals) {
        deals();
    }
});

// sanity check: content has loaded in the tab
console.log('content loaded');

Takže som si istý, že budem musieť používať chrome.skladovanie.dostať nejako, ale nemôžem prísť na to presne.