Sorting through an array of a particular data structure in Typescript

i have a collection of devices with the following structure:


export interface Device {
    id:                      Number;
    tracker_status?:         Trackerstatus;
}


export interface Trackerstatus {
    last_update?: Date;
    battery_low?: any;
}

when applying a filter like this:

function filterDevices(device: any) {
    if (device.id == 5){
        return true;
    }else{
        return false;
    }
}

everything works as expected.

now, my intention is to use a different filter that looks like this:

function filterDevices(device: any) {
  if (device.tracker_status.battery_low == "true"){
    return true;
  }else{
  return false;
  }
}

however, when using this new filter, I end up getting an empty list without any error messages. What could be the issue?

my ultimate goal is to display the filtered data in an Angular table. This is how I am currently using the filter:

devices: Device[] = data.filter(filterDevices);

Answer №1

Are you verifying against the value "true"? Have you considered checking if the

device.tracker_status.battery_low
property is actually a boolean or a string?

Keep in mind that both true == "true" and false == "true" will result in false.

console.log(true == "true");
console.log(false == "true");

I recommend implementing the following function:

function filterDevices(device: any) {
  return !!(device?.tracker_status?.battery_low);
}
  1. Learn more about the double-negation operator !! here.
  2. Find out more about the optional-chaining operator ?. here.

Answer №2

discovered the resolution after reviewing console logs

noticed that checking if tracker status is not null resolved the issue, as not all devices have it

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