I don't understand, how is the second one used?
I think I understand it. If a return type is described as x is y, then typescript assumes that if the function returns true x is y.
x is y
x
y
declare const x: y | z; if (isY(x)) { // `x` is `y`; } // `x` is `y | z`
However, with asserts x is y, typescript will assume that the function will throw if x isn't y.
asserts x is y
declare const x: y | z; // will throw if `x` isn't `y` assertIsY(x); // `x` is `y`
Super cool!
Yeah, that is true, it's upto you to do an exhaustive check on whether an object is of that type before returning true.
Yeah, I understood the concept, I was just confused by the difference of asserts x is y vs x is y
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I don't understand, how is the second one used?
I think I understand it. If a return type is described as
x is y, then typescript assumes that if the function returns truexisy.However, with
asserts x is y, typescript will assume that the function will throw ifxisn'ty.Super cool!
Yeah, that is true, it's upto you to do an exhaustive check on whether an object is of that type before returning true.
Yeah, I understood the concept, I was just confused by the difference of
asserts x is yvsx is y