Function: safe()
Call Signature
safe<
F,P,R>(fn): (...params) =>Result<R,unknown>
Transform a function which may throw an error into one with an identical call signature except that it will return a Result instead of throwing an error.
This allows you to handle the error locally with all the normal Result tools rather than having to catch an exception. Where the tryOr and tryOrElse functions are useful for a single call, this is useful to make a new version of a function to be used repeatedly.
This overload absorbs all exceptions into an Err with the type unknown. If you want to transform the error immediately rather than using a combinator, see the other overload.
Examples
The JSON.parse method will throw if the string passed to it is invalid. You can use this safe method to transform it into a form which will not throw:
import { safe } from 'true-myth/task';
const parse = safe(JSON.parse);
let result = parse(`"ill-formed gobbledygook'`);
console.log(result.toString()); // Err(SyntaxError: Unterminated string in JSON at position 25)You could do this once in a utility module and then require that all JSON parsing operations in your code use this version instead.
Type Parameters
F
F extends AnyFunction
P
P extends never[]
R
R extends unknown
Parameters
fn
F
The function which may throw, which will be wrapped.
Returns
(...
params):Result<R,unknown>
Parameters
params
...P
Returns
Result<R, unknown>
Call Signature
safe<
F,P,R,E>(fn,handleErr): (...params) =>Result<R,E>
Transform a function which may throw an error into one with an identical call signature except that it will return a Result instead of throwing an error.
This allows you to handle the error locally with all the normal Result tools rather than having to catch an exception. Where the tryOr and tryOrElse functions are useful for a single call, this is useful to make a new version of a function to be used repeatedly.
This overload allows you to transform the error immediately, using the second argument.
Examples
The JSON.parse method will throw if the string passed to it is invalid. You can use this safe method to transform it into a form which will not throw, wrapping it in a custom error :
import { safe } from 'true-myth/task';
class ParsingError extends Error {
name = 'ParsingError';
constructor(error: unknown) {
super('Parsing error.', { cause: error });
}
}
const parse = safe(JSON.parse, (error) => {
return new ParsingError(error);
});
let result = parse(`"ill-formed gobbledygook'`);
console.log(result.toString()); // Err(SyntaxError: Unterminated string in JSON at position 25)You could do this once in a utility module and then require that all JSON parsing operations in your code use this version instead.
Type Parameters
F
F extends AnyFunction
P
P extends never[]
R
R extends unknown
E
E
Parameters
fn
F
The function which may throw, which will be wrapped.
handleErr
(error) => E
A function to use to transform an unknown error into a known error type.
Returns
(...
params):Result<R,E>
Parameters
params
...P
Returns
Result<R, E>