return data from a Promise

Asked Mar 12 '19 at 09:59

Active Mar 12 '19 at 09:59

Viewed 17 times

I am Relatively a new programmer. and I am trying to retrieve a specific id value from a promise. I want a specific value inside this promise, device.deviceId , but I am not able to take it out separately and use it in the code. Tried to use a global variable and assign the value to global variable but since it is asynchronous, not able to update the value. can someone help?

let dev


const videoSelecter = navigator.mediaDevices.enumerateDevices()
.then(devices => {

devices.forEach(function(device) {

if (device.kind == "videoinput" && device.label=="Doccamera (2b19:0200)") {  
    dev=device.deviceId
   console.log("updated device ID", dev)
   return dev  
}
});
return dev
})

dev variable gets me the id but is not able to use it outside this block.

videoSelecter returns value

> Promise {<pending>}
> __proto__: Promise [[PromiseStatus]]: "resolved" [[PromiseValue]]: "14aa34325245"

I am trying to access the value in [[PromiseValue]]

asked Mar 12 '19 at 09:59

Harry

Put all code that depends on the extracted value into a `.then` – CertainPerformance Mar 12 '19 at 09:59
I dont understand. can you please explain? – Harry Mar 12 '19 at 10:01
See the linked question. `videoSelecter` is populated synchronously, but you need the data that's retrieved asynchronously. Put everything that depends on the asynchronous data in the `.then`, not outside – CertainPerformance Mar 12 '19 at 10:03
I am using the data from this function in another function. is there anyway to retrieve this value and store it and use it later on? – Harry Mar 12 '19 at 10:05
Yes, consume the Promise in a `.then` in the other function – CertainPerformance Mar 12 '19 at 10:06
Really sorry to ask this. but can you give me a sample? – Harry Mar 12 '19 at 10:08
Please read the canonical – CertainPerformance Mar 12 '19 at 10:08
i dont understand how to use .then to get that value – Harry Mar 12 '19 at 10:08
canonical as in? – Harry Mar 12 '19 at 10:12

return data from a Promise

0 Answers0