This is sort of by design. Generally speaking Object.prototype.toString() does not accept parameters, I think the only "standard" implementation which takes par

This is sort of by design. Generally speaking Object.prototype.toString() does not accept parameters, I think the only "standard" implementation which takes parameters is Number.prototype.toString(). You can overwrite .toString with your customized functions, but doing so is full of risks which can basiclaly be summed up to performance overhead and unexpected behaviour due to how you're not really in control of an object's state... As you sort of point out here. I know it's very tempting for people coming from OOP languages to use their own custom toString functions, but you really shouldn't. If you really need a string version of an object for debugging purposes you should instead get it through JSON.stringify. This is partly because .toString() isn't really meant to be used by you in JS. You can, and in a few cases it may make sense, but it's usually unnecessary because JS will do it automatically if you simply wrap your non-string primitives in the string where you want to use them. In general it's better to work with objects directly and not think of them as "classes". I think (and this is my opinion which people are going to disagree with) in general you're far better off by very rarely using classes at all in TS. There are obviously edge cases where you're going to need classes, but for 95% of your code they are going to be very unnecessary and often make it much harder for developers who may not primarily work with JS or another weakly typed language. Part of this is because classes aren't actually classes, but mainly it's because you can almost always achieve what you want with an interface or even a Type in a manner that is usually more efficient, more maintainable and easier to test because of it's decoupled nature. I have this opinion after working with JS in both the back-end and front-end for over a decade and seeing how horrible things can go wrong because we all write shitty code on a thursday afternoon, and because JS often won't work like many people from C#, Java or similar backgrounds might expect.