i have used chrome.storage.sync.set to init data when my extensions install,but i cannot read them in background,js [duplicate]

chrome.runtime.onInstalled.addListener{
let urlobj={}
chrome.storage.sync.set(urlobj}

chrome.alarms.create("everyDay",{when:Date.now(),periodInMinutes:1})
chrome.alarms.onAlarm.addListener((alarm)=>{
        chrome.storage.sync.get(urlobj,(data)=>{
            console.log("is reading urlobj"+data)
        })
)

I run on chrome,the devtool say that Error in event handler: ReferenceError: urlobj is not definederro at chrome.storage.sync.get(urlobj).How can read the storage?And why i cannot see storage in devtool?