Determining type based on it's props-CodePudding

I have these two types:

export type Equipment = {
  id: string;
  name: string;
  path: WorkCenter[];
  key?: string;
  pathToElement?: string[];
  machine_id?: StatesData.MachineMapping['machine_id'];
  machine_codes?: StatesData.MachineMapping['machine_codes'];
  timeout_s?: StatesData.MachineMapping['timeout_s'];
  stateMachines?: StatesData.MachineState['machines'];
};

export type WorkCenter = {
  id: string;
  name: string;
  children?: Equipment[];
  key?: string;
  pathToElement?: string[];
  stateMachines?: StatesData.MachineState['machines'];
};

At one point in my code, I get a variable that can either be of type Equipment, or WorkCenter.

How can I determine which it is? Depending on whether it's Equipment or WorkCenter, I need different logic to happen.

So far I am accepting this:

args: Equipment | WorkCenter

But can't think of a simple way to test which type this is.

Doing typeof would make most sense, but it's doesn't work for ts types, so won't work. I also can't just test for a property existing only on Equipment, since ts will see it as not a union. What am I missing?

CodePudding user response：

I also can't just test for a property existing only on Equipment, since ts will see it as not a union.

Using square bracket notation allows you to test without TS complaining

type TypeOne = {
  path: string;
};

type TypeTwo = {
  child: string;
};

const testIt = (t: TypeOne | TypeTwo) => {
  console.log(t['child']);
}