React Typescript: Cannot read properties of undefined-CodePudding

The console is showing a new Object but I still get the error

const GetNo = (): string => {
        console.log(record);
        if (record.no !== "")
            return record.no;   //<-- Cannot read properties of undefined
        else
            return todos[todos.length - 1].no   1;
    }

console:

EDIT: record is type of object (see picture above) and im creating it via Button onClick where i modify a state this.setState({ selectedRecord: new ToDoClass() . After that I redner the FC with the form.

EDIT 2: I tried the new Syntax:

const GetNo = (): string => {
        if (record == null) {
            console.log("1");
            return "2";
        }
        else if (record.no != null) {
            console.log("2");
            return record.no;
        }
        else {
            console.log("3");
            return todos[todos.length - 1].no   1;
        }
    }

and when the record is: new ToDoClass() it return in the console a 2 but it should go inside the first statement?!

CodePudding user response：

Your object record is defined outside of the function and may not be initialized at the execution time of the function.

I recommend you to:

Pass the object as a parameter of the function
Check that record is defined

By the way if you're using Typescript and there is a possibility that the record is not defined when passed to the function, you should get a warning at the line where you call GetNo(record).

const GetNo = (record: Record): string => {
   if (record) {
     // ...
   }
}

I hope it will be helpful!

CodePudding user response：

I don't know why it behaves like this but I solved it with a Try-Catch statement.

const GetNo = (): string => {
   try {
      if (record.no !== "")
         return record.no;
      else
         return todos[todos.length - 1].no   1;
   }
   catch {
      return "0";
   }
}