chrome.alarms

Description: Use the chrome.alarms module to schedule code to run periodically or at a specified time in the future.
Availability: Google Chrome 22
Permissions: "alarms"
Learn more: Event Pages

chrome.alarms reference

Types

Alarm

properties of Alarm

name ( string )
Name of this alarm.
scheduledTime ( double )
Time at which this alarm was scheduled to fire, in milliseconds past the epoch (e.g. Date.now() + n). For performance reasons, the alarm may have been delayed an arbitrary amount beyond this.
periodInMinutes ( optional double )
If not null, the alarm is a repeating alarm and will fire again in periodInMinutes minutes.

Methods

create

chrome.alarms.create(string name, object alarmInfo)

Creates an alarm. Near the time(s) specified by alarmInfo, the onAlarm event is fired. If there is another alarm with the same name (or no name if none is specified), it will be cancelled and replaced by this alarm.

In order to reduce the load on the user's machine, Chrome limits alarms to at most once every 1 minute but may delay them an arbitrary amount more. That is, setting delayInMinutes or periodInMinutes to less than 1 will not be honored and will cause a warning. when can be set to less than 1 minute after "now" without warning but won't actually cause the alarm to fire for at least 1 minute.

To help you debug your app or extension, when you've loaded it unpacked, there's no limit to how often the alarm can fire.

Parameters

name ( optional string )
Optional name to identify this alarm. Defaults to the empty string.
alarmInfo ( object )
Describes when the alarm should fire. The initial time must be specified by either when or delayInMinutes (but not both). If periodInMinutes is set, the alarm will repeat every periodInMinutes minutes after the initial event. If neither when or delayInMinutes is set for a repeating alarm, periodInMinutes is used as the default for delayInMinutes.
when ( optional double )
Time at which the alarm should fire, in milliseconds past the epoch (e.g. Date.now() + n).
delayInMinutes ( optional double )
Length of time in minutes after which the onAlarm event should fire.

periodInMinutes ( optional double )
If set, the onAlarm event should fire every periodInMinutes minutes after the initial event specified by when or delayInMinutes. If not set, the alarm will only fire once.

get

chrome.alarms.get(string name, function callback)

Retrieves details about the specified alarm.

Parameters

name ( optional string )
The name of the alarm to get. Defaults to the empty string.
callback ( function )

Callback

The callback parameter should specify a function that looks like this: 

function(Alarm alarm) {...};
alarm ( Alarm )

getAll

chrome.alarms.getAll(function callback)

Gets an array of all the alarms.

Parameters

callback ( function )

Callback

The callback parameter should specify a function that looks like this: 

function(array of Alarm alarms) {...};
alarms ( array of Alarm )

clear

chrome.alarms.clear(string name)

Clears the alarm with the given name.

Parameters

name ( optional string )
The name of the alarm to clear. Defaults to the empty string.

clearAll

chrome.alarms.clearAll()

Clears all alarms.

Events

onAlarm

chrome.alarms.onAlarm.addListener(function(Alarm alarm) {...});

Fired when an alarm has elapsed. Useful for event pages.

Listener Parameters

alarm ( Alarm )
The alarm that has elapsed.

Sample Extensions that use chrome.alarms

  • Event Page Example – Demonstrates usage and features of the event page
  • Google Mail Checker – Displays the number of unread messages in your Google Mail inbox. You can also click the button to open your inbox.