Question

I’ve been working on creating a ambient definitions file for flot as an exercise in learning some TypeScript, but I’ve encountered this problem multiple times in the documentation for flot (in the axis options):

ticks: null or number or ticks array or (fn: axis -> ticks array) 

So I could do this in my axisOptions interface:

interface axisOptions {
    ticks?: any;
}

Which covers all possible options, but is there a better way to restrict it to a number, an array (of numbers) or a function, but not anything else?

Answer 1

You can’t currently specify multiple types – in fact this is the perfect use of the dynamic any type because although it isn’t “anything” it is certainly dynamic.

To enforce the types on a dynamic type, you would have to check it – like in this example:

function example (input?: any) {
    alert(typeof input);
    if (typeof input !== 'undefined' && typeof input !== 'string' && typeof input !== 'number') {
        alert('no');
        return;
    }

    alert('yes');
}

example(true);
example('Okay');
example();