unknownutil
v3.18.1
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unknownutil
A utility pack for handling unknown
type.
[!WARNING]
The package on deno.land and npm is deprecated. Use the package on jsr.io instead.
deno add @core/unknownutil npx jsr add @core/unknownutil
Install
Install via npm:
npm install --save unknownutil
Usage
It provides is
module for type predicate functions and assert
, ensure
, and
maybe
helper functions.
is*
Type predicate function is a function which returns true
if a given value is
expected type. For example, isString
(or is.String
) returns true
if a
given value is string
.
import { is } from "unknownutil";
const a: unknown = "Hello";
if (is.String(a)) {
// 'a' is 'string' in this block
}
For more complex types, you can use is*Of
(or is.*Of
) functions like:
import { is, PredicateType } from "unknownutil";
const isArticle = is.ObjectOf({
title: is.String,
body: is.String,
refs: is.ArrayOf(
is.UnionOf([
is.String,
is.ObjectOf({
name: is.String,
url: is.String,
}),
]),
),
createTime: is.OptionalOf(is.InstanceOf(Date)),
updateTime: is.OptionalOf(is.InstanceOf(Date)),
});
// Infer the type of `Article` from the definition of `isArticle`
type Article = PredicateType<typeof isArticle>;
const a: unknown = {
title: "Awesome article",
body: "This is an awesome article",
refs: [{ name: "Deno", url: "https://deno.land/" }, "https://github.com"],
};
if (isArticle(a)) {
// a is narrowed to the type of `isArticle`
console.log(a.title);
console.log(a.body);
for (const ref of a.refs) {
if (is.String(ref)) {
console.log(ref);
} else {
console.log(ref.name);
console.log(ref.url);
}
}
}
Additionally, you can manipulate the predicate function returned from
isObjectOf
with isPickOf
, isOmitOf
, isPartialOf
, and isRequiredOf
similar to TypeScript's Pick
, Omit
, Partial
, Required
utility types.
import { is } from "unknownutil";
const isArticle = is.ObjectOf({
title: is.String,
body: is.String,
refs: is.ArrayOf(
is.UnionOf([
is.String,
is.ObjectOf({
name: is.String,
url: is.String,
}),
]),
),
createTime: is.OptionalOf(is.InstanceOf(Date)),
updateTime: is.OptionalOf(is.InstanceOf(Date)),
});
const isArticleCreateParams = is.PickOf(isArticle, ["title", "body", "refs"]);
// is equivalent to
//const isArticleCreateParams = is.ObjectOf({
// title: is.String,
// body: is.String,
// refs: is.ArrayOf(
// is.UnionOf([
// is.String,
// is.ObjectOf({
// name: is.String,
// url: is.String,
// }),
// ]),
// ),
//});
const isArticleUpdateParams = is.OmitOf(isArticleCreateParams, ["title"]);
// is equivalent to
//const isArticleUpdateParams = is.ObjectOf({
// body: is.String,
// refs: is.ArrayOf(
// is.UnionOf([
// is.String,
// is.ObjectOf({
// name: is.String,
// url: is.String,
// }),
// ]),
// ),
//});
const isArticlePatchParams = is.PartialOf(isArticleUpdateParams);
// is equivalent to
//const isArticlePatchParams = is.ObjectOf({
// body: is.OptionalOf(is.String),
// refs: is.OptionalOf(is.ArrayOf(
// is.UnionOf([
// is.String,
// is.ObjectOf({
// name: is.String,
// url: is.String,
// }),
// ]),
// )),
//});
const isArticleAvailableParams = is.RequiredOf(isArticle);
// is equivalent to
//const isArticlePutParams = is.ObjectOf({
// body: is.String,
// refs: is.ArrayOf(
// is.UnionOf([
// is.String,
// is.ObjectOf({
// name: is.String,
// url: is.String,
// }),
// ]),
// ),
// createTime: is.InstanceOf(Date),
// updateTime: is.InstanceOf(Date),
//});
If you need an union type or an intersection type, use isUnionOf
and
isIntersectionOf
like:
import { is } from "unknownutil";
const isFoo = is.ObjectOf({
foo: is.String,
});
const isBar = is.ObjectOf({
bar: is.String,
});
const isFooOrBar = is.UnionOf([isFoo, isBar]);
// { foo: string } | { bar: string }
const isFooAndBar = is.IntersectionOf([isFoo, isBar]);
// { foo: string } & { bar: string }
assert
The assert
function does nothing if a given value is expected type. Otherwise,
it throws an AssertError
exception like:
import { assert, is } from "unknownutil";
const a: unknown = "Hello";
// `assert` does nothing or throws an `AssertError`
assert(a, is.String);
// a is now narrowed to string
// With custom message
assert(a, is.String, { message: "a must be a string" });
ensure
The ensure
function return the value as-is if a given value is expected type.
Otherwise, it throws an AssertError
exception like:
import { ensure, is } from "unknownutil";
const a: unknown = "Hello";
// `ensure` returns `string` or throws an `AssertError`
const _: string = ensure(a, is.String);
// With custom message
const __: string = ensure(a, is.String, { message: "a must be a string" });
maybe
The maybe
function return the value as-is if a given value is expected type.
Otherwise, it returns undefined
that suites with
nullish coalescing operator (??
)
like:
import { is, maybe } from "unknownutil";
const a: unknown = "Hello";
// `maybe` returns `string | undefined` so it suites with `??`
const _: string = maybe(a, is.String) ?? "default value";
Migration
See GitHub Wiki for migration to v3 from v2 or v2 from v1.
License
The code follows MIT license written in LICENSE. Contributors need to agree that any modifications sent in this repository follow the license.