I require clarity on this befuddling syntax that feels like descending into

I came across this example in the official documentation at https://angular.io/guide/form-validation#custom-validators

 return (control: AbstractControl): {[key: string]: any} => {
    const forbidden = nameRe.test(control.value);
    return forbidden ? {'forbiddenName': {value: control.value}} : null;
 };

Can someone help me understand how to interpret this code snippet?

 return (control: AbstractControl): {[key: string]: any} => {
    return ...
 }

It seems like it's returning a JavaScript object (control : object), but then why is there a lambda function?

The issue here is not what the function does, as that is explained in the documentation, but rather the syntax of the return statement.

Edit: I just learned that you can create a function like that, so now it makes sense to me.

Could someone please explain this to me? Thank you.

Answer №1

When invoked, it generates a function that takes in a parameter labeled control with the specified type of AbstractControl (control: AbstractControl). The resulting function then produces an object that can be accessed by string keys and contains values of any type ({[key: string]: any}). This function is implemented as an arrow function (=>)

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