@praha/byethrow
provides two distinct import methods to balance efficient development with optimal bundle size. Both approaches fully support tree-shaking, ensuring that unused features are automatically excluded from your final bundle.
Result
)For verbose and explicit code that prioritizes clarity, use the Result
namespace:
import { import Result
Result } from '@praha/byethrow';
const const validateUser: (id: string) => Result.Failure<Error> | Result.Success<string>
validateUser = (id: string
id : string) => {
if (!id: string
id .String.startsWith(searchString: string, position?: number): boolean
Returns true if the sequence of elements of searchString converted to a String is the
same as the corresponding elements of this object (converted to a String) starting at
position. Otherwise returns false.
startsWith ('u')) {
return import Result
Result .const fail: <Error>(error: Error) => Result.Result<never, Error> (+1 overload)
fail (new var Error: ErrorConstructor
new (message?: string, options?: ErrorOptions) => Error (+1 overload)
Error ('Invalid ID format'));
}
return import Result
Result .const succeed: <string>(value: string) => Result.Result<string, never> (+1 overload)
succeed (id: string
id );
};
const const result: Result.Result<{
id: string;
name: string;
}, Error>
result = import Result
Result .const pipe: <Result.Result<string, never>, Result.Result<string, Error>, Result.Result<{
id: string;
name: string;
}, Error>>(a: Result.Result<string, never>, ab: (a: Result.Result<string, never>) => Result.Result<string, Error>, bc: (b: Result.Result<string, Error>) => Result.Result<{
id: string;
name: string;
}, Error>) => Result.Result<{
id: string;
name: string;
}, Error> (+25 overloads)
pipe (
import Result
Result .const succeed: <string>(value: string) => Result.Result<string, never> (+1 overload)
succeed ('u123'),
import Result
Result .const andThen: <Result.Result<string, never>, Result.Failure<Error> | Result.Success<string>>(fn: (a: string) => Result.Failure<Error> | Result.Success<string>) => (result: Result.Result<string, never>) => Result.Result<string, Error> (+1 overload)
andThen (const validateUser: (id: string) => Result.Failure<Error> | Result.Success<string>
validateUser ),
import Result
Result .const map: <Result.Result<string, Error>, {
id: string;
name: string;
}>(fn: (a: string) => {
id: string;
name: string;
}) => (result: Result.Result<string, Error>) => Result.Result<{
id: string;
name: string;
}, Error> (+1 overload)
map (id: string
id => ({ id: string
id , name: string
name : 'John Doe' }))
);
if (import Result
Result .const isSuccess: <{
id: string;
name: string;
}>(result: Result.Result<{
id: string;
name: string;
}, unknown>) => result is Result.Success<{
id: string;
name: string;
}>
Type guard to check if a
Result
is a
Success
.
@function@typeParamT
- The type of the success value.@paramresult
- The Result
to check.@returnstrue
if the result is a Success
, otherwise false
.@exampleimport { Result } from '@praha/byethrow';
const result: Result.Result<number, string> = { type: 'Success', value: 10 };
if (Result.isSuccess(result)) {
console.log(result.value); // Safe access to value
}
@categoryType
Guards isSuccess (const result: Result.Result<{
id: string;
name: string;
}, Error>
result )) {
var console: Console
The console
module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console
class with methods such as console.log()
, console.error()
and console.warn()
that can be used to write to any Node.js stream.
- A global
console
instance configured to write to process.stdout
and
process.stderr
. The global console
can be used without importing the node:console
module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O
for
more information.
Example using the global console
:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console
class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@seesource console .Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stdout
with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()
).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format()
for more information.
@sincev0
.1.100 log (const result: Result.Success<{
id: string;
name: string;
}>
result .value: {
id: string;
name: string;
}
value );
}
R
)For concise code that favors brevity, use the R
alias:
import { import R
R } from '@praha/byethrow';
const const validateUser: (id: string) => R.Failure<Error> | R.Success<string>
validateUser = (id: string
id : string) => {
if (!id: string
id .String.startsWith(searchString: string, position?: number): boolean
Returns true if the sequence of elements of searchString converted to a String is the
same as the corresponding elements of this object (converted to a String) starting at
position. Otherwise returns false.
startsWith ('u')) {
return import R
R .const fail: <Error>(error: Error) => R.Result<never, Error> (+1 overload)
fail (new var Error: ErrorConstructor
new (message?: string, options?: ErrorOptions) => Error (+1 overload)
Error ('Invalid ID format'));
}
return import R
R .const succeed: <string>(value: string) => R.Result<string, never> (+1 overload)
succeed (id: string
id );
};
const const result: R.Result<{
id: string;
name: string;
}, Error>
result = import R
R .const pipe: <R.Result<string, never>, R.Result<string, Error>, R.Result<{
id: string;
name: string;
}, Error>>(a: R.Result<string, never>, ab: (a: R.Result<string, never>) => R.Result<string, Error>, bc: (b: R.Result<string, Error>) => R.Result<{
id: string;
name: string;
}, Error>) => R.Result<{
id: string;
name: string;
}, Error> (+25 overloads)
pipe (
import R
R .const succeed: <string>(value: string) => R.Result<string, never> (+1 overload)
succeed ('u123'),
import R
R .const andThen: <R.Result<string, never>, R.Failure<Error> | R.Success<string>>(fn: (a: string) => R.Failure<Error> | R.Success<string>) => (result: R.Result<string, never>) => R.Result<string, Error> (+1 overload)
andThen (const validateUser: (id: string) => R.Failure<Error> | R.Success<string>
validateUser ),
import R
R .const map: <R.Result<string, Error>, {
id: string;
name: string;
}>(fn: (a: string) => {
id: string;
name: string;
}) => (result: R.Result<string, Error>) => R.Result<{
id: string;
name: string;
}, Error> (+1 overload)
map (id: string
id => ({ id: string
id , name: string
name : 'John Doe' }))
);
if (import R
R .const isSuccess: <{
id: string;
name: string;
}>(result: R.Result<{
id: string;
name: string;
}, unknown>) => result is R.Success<{
id: string;
name: string;
}>
Type guard to check if a
Result
is a
Success
.
@function@typeParamT
- The type of the success value.@paramresult
- The Result
to check.@returnstrue
if the result is a Success
, otherwise false
.@exampleimport { Result } from '@praha/byethrow';
const result: Result.Result<number, string> = { type: 'Success', value: 10 };
if (Result.isSuccess(result)) {
console.log(result.value); // Safe access to value
}
@categoryType
Guards isSuccess (const result: R.Result<{
id: string;
name: string;
}, Error>
result )) {
var console: Console
The console
module provides a simple debugging console that is similar to the
JavaScript console mechanism provided by web browsers.
The module exports two specific components:
- A
Console
class with methods such as console.log()
, console.error()
and console.warn()
that can be used to write to any Node.js stream.
- A global
console
instance configured to write to process.stdout
and
process.stderr
. The global console
can be used without importing the node:console
module.
Warning: The global console object's methods are neither consistently
synchronous like the browser APIs they resemble, nor are they consistently
asynchronous like all other Node.js streams. See the note on process I/O
for
more information.
Example using the global console
:
console.log('hello world');
// Prints: hello world, to stdout
console.log('hello %s', 'world');
// Prints: hello world, to stdout
console.error(new Error('Whoops, something bad happened'));
// Prints error message and stack trace to stderr:
// Error: Whoops, something bad happened
// at [eval]:5:15
// at Script.runInThisContext (node:vm:132:18)
// at Object.runInThisContext (node:vm:309:38)
// at node:internal/process/execution:77:19
// at [eval]-wrapper:6:22
// at evalScript (node:internal/process/execution:76:60)
// at node:internal/main/eval_string:23:3
const name = 'Will Robinson';
console.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to stderr
Example using the Console
class:
const out = getStreamSomehow();
const err = getStreamSomehow();
const myConsole = new console.Console(out, err);
myConsole.log('hello world');
// Prints: hello world, to out
myConsole.log('hello %s', 'world');
// Prints: hello world, to out
myConsole.error(new Error('Whoops, something bad happened'));
// Prints: [Error: Whoops, something bad happened], to err
const name = 'Will Robinson';
myConsole.warn(`Danger ${name}! Danger!`);
// Prints: Danger Will Robinson! Danger!, to err
@seesource console .Console.log(message?: any, ...optionalParams: any[]): void (+1 overload)
Prints to stdout
with newline. Multiple arguments can be passed, with the
first used as the primary message and all additional used as substitution
values similar to printf(3)
(the arguments are all passed to util.format()
).
const count = 5;
console.log('count: %d', count);
// Prints: count: 5, to stdout
console.log('count:', count);
// Prints: count: 5, to stdout
See util.format()
for more information.
@sincev0
.1.100 log (const result: R.Success<{
id: string;
name: string;
}>
result .value: {
id: string;
name: string;
}
value );
}
@praha/byethrow
achieves complete tree-shaking support:
// Example: Usage in a small application
import { import R
R } from '@praha/byethrow';
// Only these features are actually used
const const parseNumber: (input: string) => R.Result<number, Error>
parseNumber = import R
R .try<(input: string) => number, Error>(options: {
try: (input: string) => number;
catch: (error: unknown) => Error;
}): (input: string) => R.Result<number, Error> (+7 overloads)
export try
Wraps a function execution (sync or async) or a Promise in a
Result
or
ResultAsync
type,
capturing errors and returning them in a structured way.
You can use either a custom catch
handler or rely on the safe: true
option
to assume the function cannot throw.
@function@typeParamT
- The function type to execute (sync or async) or a Promise type.@typeParamE
- The error type to return if catch
is used.@exampleSync
try-catch
import { Result } from '@praha/byethrow';
const fn = Result.try({
try: (x: number) => {
if (x < 0) throw new Error('Negative!');
return x * 2;
},
catch: (error) => new Error('Oops!', { cause: error }),
});
const result = fn(5); // Result.Result<number, Error>
@exampleSync
try-catch with immediate execution
import { Result } from '@praha/byethrow';
const result = Result.try({
immediate: true,
try: () => {
const x = Math.random() * 10 - 5;
if (x < 0) throw new Error('Negative!');
return x * 2;
},
catch: (error) => new Error('Oops!', { cause: error }),
});
// result is Result<number, Error>
@exampleSync
safe
import { Result } from '@praha/byethrow';
const fn = Result.try({
safe: true,
try: (x: number) => x + 1,
});
const result = fn(1); // Result.Result<number, never>
@exampleSync
safe with immediate execution
import { Result } from '@praha/byethrow';
const result = Result.try({
safe: true,
immediate: true,
try: () => Math.random() + 1,
});
// result is Result<number, never>
@exampleAsync
try-catch
import { Result } from '@praha/byethrow';
const fn = Result.try({
try: async (id: string) => await fetch(`/api/data/${id}`),
catch: (error) => new Error('Oops!', { cause: error }),
});
const result = await fn('abc'); // Result.ResultAsync<Response, Error>
@exampleAsync
try-catch with immediate execution
import { Result } from '@praha/byethrow';
const result = Result.try({
immediate: true,
try: () => fetch('/api/data'),
catch: (error) => new Error('Fetch failed', { cause: error }),
});
// result is ResultAsync<Response, Error>
@exampleAsync
safe
import { Result } from '@praha/byethrow';
const fn = Result.try({
safe: true,
try: async () => await Promise.resolve('ok'),
});
const result = await fn(); // Result.ResultAsync<string, never>
@exampleAsync
safe with immediate execution
import { Result } from '@praha/byethrow';
const result = Result.try({
safe: true,
immediate: true,
try: () => Promise.resolve('ok'),
});
// result is ResultAsync<string, never>
@categoryCreators
try ({
try: (input: string) => number
try : (input: string
input : string) => function parseInt(string: string, radix?: number): number
Converts a string to an integer.
@paramstring
A string to convert into a number.@paramradix
A value between 2 and 36 that specifies the base of the number in string
.
If this argument is not supplied, strings with a prefix of '0x' are considered hexadecimal.
All other strings are considered decimal. parseInt (input: string
input , 10),
catch: (error: unknown) => Error
catch : () => new var Error: ErrorConstructor
new (message?: string, options?: ErrorOptions) => Error (+1 overload)
Error ('Invalid number')
});
// In this case, only the minimal code required for parseNumber
// is included in the bundle, while other features (combine, pipe, etc.) are excluded
Result
if you prefer explicit and descriptive naming that clearly indicates the purpose of each operationR
if you prefer fewer keystrokes and more concise code for faster developmentWe strongly recommend against mixing Result
and R
within the same codebase. Choose one approach and stick with it consistently throughout your project to maintain code readability and consistency.
// @filename: mixed-imports.ts
// ❌ Don't mix approaches - this creates inconsistent code
import { import Result
Result , import R
R } from '@praha/byethrow';
const const validateId: (id: string) => Result.Result<string, never>
validateId = (id: string
id : string) => {
return import Result
Result .const succeed: <string>(value: string) => Result.Result<string, never> (+1 overload)
succeed (id: string
id ); // Using Result
};
const const processData: Result.Result<string, never>
processData = import R
R .const pipe: <Result.Result<string, never>, Result.Result<string, never>>(a: Result.Result<string, never>, ab: (a: Result.Result<string, never>) => Result.Result<string, never>) => Result.Result<string, never> (+25 overloads)
pipe ( // Using R
import R
R .const succeed: <string>(value: string) => Result.Result<string, never> (+1 overload)
succeed ('data'),
import R
R .const andThen: <Result.Result<string, never>, Result.Result<string, never>>(fn: (a: string) => Result.Result<string, never>) => (result: Result.Result<string, never>) => Result.Result<string, never> (+1 overload)
andThen (const validateId: (id: string) => Result.Result<string, never>
validateId )
);
// @filename: consistent-imports.ts
// ✅ Choose one approach and use it consistently
import { import Result
Result } from '@praha/byethrow';
const const validateId: (id: string) => Result.Result<string, never>
validateId = (id: string
id : string) => {
return import Result
Result .const succeed: <string>(value: string) => Result.Result<string, never> (+1 overload)
succeed (id: string
id );
};
const const processData: Result.Result<string, never>
processData = import Result
Result .const pipe: <Result.Result<string, never>, Result.Result<string, never>>(a: Result.Result<string, never>, ab: (a: Result.Result<string, never>) => Result.Result<string, never>) => Result.Result<string, never> (+25 overloads)
pipe (
import Result
Result .const succeed: <string>(value: string) => Result.Result<string, never> (+1 overload)
succeed ('data'),
import Result
Result .const andThen: <Result.Result<string, never>, Result.Result<string, never>>(fn: (a: string) => Result.Result<string, never>) => (result: Result.Result<string, never>) => Result.Result<string, never> (+1 overload)
andThen (const validateId: (id: string) => Result.Result<string, never>
validateId )
);
Regardless of which method you choose, bundlers will automatically optimize your code, ensuring only the necessary features are included in your final bundle.