使用 Alarms API 调度任务
在 Manifest V3 服务工作线程中使用 chrome.alarms，可靠地运行周期性和延迟的后台任务。
使用 Alarms API 调度任务 是 CoddyKit 上的免费 Browser Extensions Development (Chrome & Edge) 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Browser Extensions Development (Chrome & Edge) 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Browser Extensions Development (Chrome & Edge) 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Why Not setInterval
In Manifest V3 the service worker unloads when idle, so setTimeout and setInterval are unreliable for scheduled work. The alarms API survives this by waking the worker when it is time to run.
Declaring the Permission
Add the alarms permission to the manifest before using the API.
{
"permissions": ["alarms"]
}Creating a One-Time Alarm
Use alarms.create with delayInMinutes for a single delayed task.
chrome.alarms.create('cleanup', { delayInMinutes: 5 })Creating a Repeating Alarm
Add periodInMinutes to make the alarm fire again and again on a schedule.
chrome.alarms.create('sync', { periodInMinutes: 30 })Handling the Alarm
Listen for onAlarm at the top level of your service worker. The alarm object tells you which one fired.
chrome.alarms.onAlarm.addListener((alarm) => {
if (alarm.name === 'sync') {
doSync()
}
})Register Listeners at the Top Level
Because the worker restarts, register onAlarm synchronously when the script first runs, not inside an async callback, or the wake-up may be missed.
// top of background.js, runs on every wake
chrome.alarms.onAlarm.addListener(handleAlarm)Minimum Period
For packed extensions the smallest repeating period is about one minute. Shorter intervals are clamped, so do not rely on second-level timing.
chrome.alarms.create('tick', { periodInMinutes: 1 })Inspecting Alarms
Use alarms.get or alarms.getAll to check what is scheduled, useful for avoiding duplicates.
const a = await chrome.alarms.get('sync')
if (!a) chrome.alarms.create('sync', { periodInMinutes: 30 })Clearing Alarms
Remove a single alarm with clear or all of them with clearAll when a feature is turned off.
chrome.alarms.clear('sync')
chrome.alarms.clearAll()Recreating on Install
Set up your alarms in the onInstalled event so they exist from the moment the extension is installed or updated.
chrome.runtime.onInstalled.addListener(() => {
chrome.alarms.create('sync', { periodInMinutes: 30 })
})Keeping Work Short
The worker may unload soon after the alarm. Keep the task quick, persist state to storage, and avoid long-running loops that could be cut off.
Quick Check
Test your alarms knowledge.
Recap
You learned reliable scheduling:
- Use
alarms.createwith delay or period - Handle
onAlarmregistered at the top level - Respect the ~1 minute minimum period
- Inspect, clear, and recreate alarms
- Keep alarm work short
The alarms API makes background scheduling dependable under Manifest V3.
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常见问题解答
「使用 Alarms API 调度任务」课时是免费的吗？
是的 — 「使用 Alarms API 调度任务」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Browser Extensions Development (Chrome & Edge) 课程的其余内容，请升级到 CoddyKit PRO。 Browser Extensions Development (Chrome & Edge) 课程共包含 4 节课。
「使用 Alarms API 调度任务」这节课中我会学到什么？
在 Manifest V3 服务工作线程中使用 chrome.alarms，可靠地运行周期性和延迟的后台任务。 你通过在浏览器中直接运行的动手代码来练习 Browser Extensions Development (Chrome & Edge)，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Browser Extensions Development (Chrome & Edge) 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Browser Extensions Development (Chrome & Edge) 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「使用 Alarms API 调度任务」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Browser Extensions Development (Chrome & Edge) 课中编写并运行代码吗？
能。每节 Browser Extensions Development (Chrome & Edge) 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。