typescript-throws
v1.0.1
Published
Optional datatype for Typescript
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typescript-throws
A small utility class for Typescript to wrap throwable
values as return types. This is very similar to Haskell maybe
and either
. It is also similar to Rust's Result
and Option
return types.
Usage
To create a safe-by-design function, simply change your return type from <T>
to Throws<T>
and call Throws.pure(returnValue)
on your return values. Finally, replace all throw new Error
instances with Throws.pure(new Error)
.
class DivideByZeroError extends Error {
constructor(message: string) {
super(message);
this.name = "DivideByZero"
}
}
function divide(a: number, b: number): Throws<number> {
if (b === 0) {
return Throws.pure(new DivideByZeroError("Argument b is 0"));
}
return Throws.pure(a / b);
}
Opaque types
divide(5, 4) // Throws: { "value": 1.25 }
divide(3, 0) // Throws: { "value": { "name" : ... } }
Optional values
divide(5, 4).optional() // 1.25
divide(3, 0).optional() // null
Curried Bindings
// Curried
function divBy(b: number) {
return (a: number) => divide(a, b)
}
divide(50,1).bind(divBy(2)).bind(divBy(2)).bind(divBy(.5)).optional() // 25
divide(50,0).bind(divBy(2)).bind(divBy(2)).bind(divBy(.5)).shouldThrow() // true
divide(50,0).bind(divBy(2)).bind(divBy(2)).bind(divBy(.5)).unwrap() // DivideByZeroError: Argument b is 0
Many-way Bindings
divide(5,4).bindMany(divide)(4).optional() // 0.3125
divide(5,0).bindMany(divide)(4).optional() // null
Dangerous Unwrap
divide(5, 4).unwrap() // 1.25
divide(3, 0).unwrap() // DivideByZeroError: Argument b is 0
Language
pure
and bind
come from the Haskell Standard Library
Monad
and Applicative
interfaces.