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 -
Thank you for your help.
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.
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__])
Related
I'm trying to turn an array in which every element is an array containing the key, and the value(like entries), I'm trying to convert it back to an object element by the help of the method Object.fromEntries(array) but there seem to be a problem.
This is the error I get: TypeError: Object.fromEntries requires the first iterable parameter yields objects
Here's how I use the method:
const saved = JSON.parse(Object.fromEntries(localStorage.getItem(key)))
The local storage value it should retrieve:
[["$$typeof",null],["type",null],["key",null],["ref",null],["props",{"data":"a data containing collections of objects(fetched from an API)"}]
Since it might be helpful, what I'm trying to do is to store a react component(yes, I work on ReactJS) to local storage and get it back when necessary.
If you don't think that this portion of code is not the reason why this issue appears, please do let me know.
Ok, so I have a database with data sets in it. the application performs a base API call to retrieve that base data set containing all other data sets. I will receive a string variable with the name of the key I need to access so let's say const addon = "Book". However, I don't know the key name beforehand. So the following code works but I need to somehow not hard code the key parameter but rather use the string value incoming from the const addon. I am not quite sure how to do this please point me to the right documentation or explain how to achieve the wanted result.
const columns = levelOne.Book && Object.keys(levelOne.Book);
However, as the incoming param might not be "Book" but anything else it will only work for this case. It is guaranteed that there is a key-value pair where the key bears the name stored in the string value of addon.
You can use a variable as the key. For example, levelOne[variable] where variable is the string that you want to use as the key.
Also, you can get the keys through Object.keys(levelOne) and then you can set variable value from the keys array.
I have one object called bookings, and inside it I have several properties, and i want extend with Object.assign, like this:
let data = Object.assign(booking, {
hiw: event.hiw[booking.locale],
tip: event.tip[booking.locale],
start: moment(event.start).format('L')
});
But when I print the data, the result will be the same object from the source (booking), so hiw, tip and start will be ignored, but... if I try to do:
let data = Object.assign({}, {
hiw: event.hiw[booking.locale],
tip: event.tip[booking.locale],
start: moment(event.start).format('L')
});
This will work perfect.
My question is: what am I doing wrong here? Why can't I extend booking and I can extend the empty object?
That's definitely not a problem with async code, when i try to extend booking, he already exist with all properties inside.
I also was trying to use underscore extend method, and the behavior is exactly the same.
Mongoose documents (model instances) are special: they will only print properties that are present in the schema.
If properties aren't defined there, they won't show up when you console.log() them (and also not if you convert the document to a plain JS object with obj.toObject()).
This means that using Object.assign() will only work if you assign properties that are also present in the schema. Any properties that aren't declared will not be shown (nor saved to the database).
If your intention is to use the document for output, you should convert it to a proper JS object first before assigning to it:
let data = Object.assign(booking.toObject(), {
hiw : event.hiw[booking.locale],
tip : event.tip[booking.locale],
start : moment(event.start).format('L')
});
So I'm trying to save an object via the chrome.storage API. The relevant code is:
var images = null;
var storage = chrome.storage.sync;
var key = "key";
images = getImages(source);
alert(images.length); // returns 4
storage.set({key: images});
storage.get("key", function(result) {
alert(result.length); // returns undefined
});
I'm tested that immediately after the getImages() function, images is a wrapped set JQuery object with a length of 4. However, when I try to access images.length via the storage.get callback, the result is undefined.
Could someone help identify the error in how I am storing and/or retrieving this JQuery object?
Update 1:
Thank you all for your help. As clarification for the use case, I am using chrome.storage instead of localStorage because I plan to pass extension info to another script.
Fortunately, TranQ/Xan's solution has enabled me to access the array via the storage.get call.
I'm still experiencing issues working with the wrapped set JQuery object stored in the array but I'll post a separate question since the current solution encapsulates broader use cases.
TranQ's comment is on point.
Presumably, images is an array. You store that array under the "key" key.
When you execute the get() function, it returns an object populated with all key-value pairs you asked, even if you only ask for one key.
So, result is an object {key : [/* something */]}. Objects do not have a length property, and you get undefined
You need to use result.key (or result["key"]) to access your array.
I have an IndexedDB of changes. I add an item like this, and then log the result to check the key has been created successfully:
_this._idb.add('steps', step).done(function (items) {
var item = items[0];
_logger.log("ADDED STEP", { id: item.__id__, step: item }, "CT");
});
The output from this is as expected:
...as you can see, the id has been added to the object when it is stored.
However, when I query the db to getback a list of objects, using this code:
this._idb.steps.query('timestamp').bound(start, end).execute().done(function (results) {
_logger.log("Results", results, "CT");
}
I don't get the id as part of the object that is returned:
... and the lack of id makes updating and deleting impossible.
How can I get the id of the item when I query indexed db using db.js - or am I approaching this in the wrong way, and is there something else I should be doing?
(Note: I'm using TypeScript to compile the JS, but I don't think that's especially relevant to this question)
This is expected behaviour, you're only going to get the __id__ property if you don't define a keyPath in your db schema.
Because there's no keyPath defined the value is not associated with it in indexeddb, it's only added to the resulting object after it has been added, because at that point in time we know the auto-incremented value that IndexedDB has assigned to it.
Since the value isn't really part of the object I don't have any way to assign it to the object when it comes out during a query, maybe I could use the position in the array but that's more likely to be wrong than right.
If you want the ID to be persisted against the object then you need to define a keyPath as part of the object store schema and the property will be added to the resulting object and available and it will be on the object returned from a query.
Disclaimer - I wrote db.js
Looking at the source, __id__ is only defined when your keyPath is null in the add() method. From what I'm seeing, you'll never see this in a query() response.
In IDB null keyPaths are allowed only when using auto-incrementing ("out-of-line") keys. So if you're getting the object back, it should have an auto-incrementing key on it or some other keyPath.
The __ prefix in JavaScript usually means the developer intended it to be a "private" property. I'm guessing this is for internal use and you shouldn't be counting on this in your application code.
Consider using explicit, so-called "in-line" keys on your object store.
The goal of db.js is easy and simple to use. Your is advanced use case.