i have an array of devices that look like this.

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


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

applying a filter like

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

works perfectly fine.

however what i am trying to do is

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

this just returns an empty list with no error messages. what am i doing wrong?

the goal is to show the filtered data in an angular table. i am using the filter like this

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

CodePudding user response：

You're checking against the string "true". Did you check if the device.tracker_status.battery_low property is a boolean or a string?

Note that both true == "true" and false == "true" would return false.

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

I'd suggest the following

function filterDevices(device: any) {
  return !!(device?.tracker_status?.battery_low);
}

1. More about the double-negation operator !! here.
2. More about the optional-chaining operator ?. here.

CodePudding user response：

found the solution. forgot to check console logs

simply checking if tracker status is not null since not every device has it solved the problem.