Tips for receiving a linter/compiler warning when comparing a function without its call being made?

Often, I find myself making a common mistake when writing TypeScript code:

class Foo {
  constructor() { }
  public get isFoo(): boolean { return true; } // getter
  public isBar(): boolean { return false; } // normal function
}

let foo = new Foo();
if (foo.isFoo) { // This is correct as the getter returns true
  console.log("it is foo");
}
// Here is where the mistake occurs:
if (foo.isBar) { // <-isBar is defined, forgot to include ()
  console.log("it is bar"); // This will also execute 
}

Is there any way to receive a warning from a tslinter or compiler for this type of mistake?

Answer №1

The syntax in your conditional statement is completely valid, so it is not possible that there would be an issue with it.

Sometimes you may need to check if a method is declared within a conditional block and execute some code accordingly.

For instance:

class Bar {
  public isBar(): boolean {
    return true;
  }
  public get isBaz(): boolean {
    return false;
  }
}

const barInstance: Bar = new Bar();

if (bar.isBar) {
  console.log('Bar class has method isBar');
}

if (!bar.isXyz) {
  console.log('Bar class does not have method isXyz');
}

const barMethod: () => boolean = bar.isBar; // this syntax is also valid

In the example above, neither a linter nor a compiler will raise any errors for the scenarios mentioned.

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