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Discussion on: You CAN Convert your Callbacks to Promises

 
prof3ssorst3v3 profile image
Steve Griffith Author • Edited on

maximumAge doesn't keep the same timestamp with each request.
The browser will cache a coordinates object with a timestamp.
Each subsequent time you make a request, it will look at the current timestamp and compare it with the cache result's timestamp. If you have not reached the maximumAge yet then you get a copy of the coordinates object along with a current timestamp.
The position object
{
timestamp: current value for the current request
coords: { this could be the cached coords object or a new one if you are past the cached timestamp }
}
HOWEVER...
The browser is allowed to adjust the result in the interest of better battery life and lowered use of the radio antenna in the device.
It also uses the highAccuracy setting to decide what to do based on other things happening on the device. When you say that you want highAccuracy, you are really just saying that it is allowed for the device to use it, not that the device MUST use it.
The developer provides their best intention to the browser through the options object, but it is still up to the browser to interpret those settings.
Many of the HTML5 APIs work this way.

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rowild profile image
Robert Wildling

Thank you again very much, Steve!

What I observe is that the coordinate values change all the time, no matter what. So if I understand you correctly: Using maximumAge to manage the amount of geolocation points to be saved to a data store is unreliable. If I want to save a geolocation datum only every 3rd second; i need to implement my own timer.
To be honest: I do not really understand, what this setting is good for, if the browser does whatever it wants whenever it wants... :-(

However, I love your tutorials and texts and am looking forward to new stuff of yours! Thank you again! Have a good day!

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prof3ssorst3v3 profile image
Steve Griffith Author

You're very welcome.
Just bear in mind that changing the maximumAge option, the enableHighAccuracy option, or using a timer you create yourself will get similar results. The management of the radio in the phone is beyond absolute control of the JS. It will always be the device and the browser that get to make the final decision about how to use the radio - wifi, gps, etc.