How to access values from this complex JavaScript Object?

Question

I am working with AbsoluteOrientationSensor

I have an object that contains the values of the accelerometer of the phone.

The values that I need are nested inside an Symbol in the Object.

How do I access those values?

The Object Name is "message".

I have already tried this

console.log(message.__sensor__.quaternion);

But I am getting the result as "undefined".

I have never worked with the Symbol data type in JavaScript before.

The Values that I want to access are the quaternion values

This is the screenshot of the Object Structure -

The Object that I'm working with

Thank you for your help.

developer.mozilla.org/en-US/docs/Glossary/Symbol

Pranav C Balan
– Pranav C Balan

2019-03-13 19:06:03 +00:00
Commented Mar 13, 2019 at 19:06 — Pranav C Balan
– Pranav C Balan, Commented Mar 13, 2019 at 19:06

Felix Kling · Accepted Answer · 2019-03-13 19:12:17Z

3

From the documentation:

Properties

OrientationSensor.quaternion: Returns a four element Array whose elements contain the components of the unit quaternion representing the device's orientation.

So:

console.log(message.quaternion);

You can also see in the screenshot that the object itself has a getter quaternion.

I have never worked with the Symbol data type in JavaScript before.

Symbols are used for various reasons as property names, but if they are used, it almost always means that you, as a consumer of the API, are not supposed to access that value directly. Instead you should use the "public" API the object provides to access this data, such as in this case.

edited Mar 13, 2019 at 19:12

answered Mar 13, 2019 at 19:06

Felix Kling

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2 Comments

JoKeR_95 Over a year ago

Hey, thanks for the quick reply. I'm getting four values which are all undefined. Any idea why?

Felix Kling Over a year ago

Maybe you are trying to access the data before the sensor has a reading. See developer.mozilla.org/en-US/docs/Web/API/Sensor_APIs#Readings

AlexOwl · Accepted Answer · 2019-03-13 19:17:55Z

0

function GetSymbol(object, name) {
  const string = `Symbol(${name})`
  return Object.getOwnPropertySymbols(object).find(symbol => symbol.toString() === string)
}

const __sensor__ = GetSymbol(message, "__sensor__")

console.log(message[__sensor__])

answered Mar 13, 2019 at 19:17

AlexOwl

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2 Comments

AlexOwl Over a year ago

@FelixKling i thought the question was about accessing Symbol property

Felix Kling Over a year ago

Kind of, I guess ¯\_(ツ)_/¯ . On a higher level the question is about how to access the data there, and the answer is to use the public API to do so.

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