satisfies مقابل تعليق النوع

نمط التعليق النوعي

type Config = { mode: string; level: number };
const config: Config = { mode: "dark", level: 5 };
// config.mode has type string
console.log(config.mode);

كيف يبدو التوسيع

type Config = { mode: string };
const config: Config = { mode: "dark" };
// const m: "dark" = config.mode; // Error: string not assignable to "dark"
console.log(config.mode);

نمط satisfies

type Config = { mode: string; level: number };
const config = { mode: "dark", level: 5 } satisfies Config;
// config.mode has type "dark"
console.log(config.mode);

الحفاظ على الاستدلال الدقيق

type Config = { mode: string };
const config = { mode: "dark" } satisfies Config;
const m: "dark" = config.mode; // OK
console.log(m);

يستمر التحقق في كلا الأسلوبين

type Config = { level: number };
// const a: Config = { level: "x" }; // Error
// const b = { level: "x" } satisfies Config; // Error
const ok = { level: 3 } satisfies Config;
console.log(ok.level);

اكتشاف الخصائص الإضافية

type Config = { mode: string };
// const c = { mode: "dark", extar: true } satisfies Config; // Error: extar
const c = { mode: "dark" } satisfies Config;
console.log(c.mode);

الحفاظ على طبيعة tuple

type Nums = readonly number[];
const xs = [1, 2, 3] as const satisfies Nums;
// xs is a readonly tuple [1, 2, 3], validated as numbers
console.log(xs.length);

التعليق النوعي يوسّع أعضاء الاتحاد

type Config = { tier: string };
const withAnn: Config = { tier: "pro" };       // tier: string
const withSat = { tier: "pro" } satisfies Config; // tier: "pro"
console.log(withAnn.tier, withSat.tier);

الحفاظ على الإكمال التلقائي عند القراءة

type Theme = Record<string, string>;
const theme = { bg: "black", fg: "white" } satisfies Theme;
// theme.<autocomplete shows bg and fg>
console.log(theme.bg, theme.fg);

الاختيار بين الأسلوبين

type Config = { mode: string };
// Want wide type for reassignment flexibility -> annotation
let a: Config = { mode: "dark" };
// Want exact literals for later indexing -> satisfies
const b = { mode: "dark" } satisfies Config;
console.log(a.mode, b.mode);

ملخص مقارن

type C = { color: string; size: number };
const widened: C = { color: "red", size: 1 };
const exact = { color: "red", size: 1 } satisfies C;
console.log(widened.color, exact.color);

اختبار سريع: satisfies مقابل التعليق النوعي

مراجعة: satisfies مقابل التعليق النوعي

type C = { mode: string };
const c = { mode: "dark" } satisfies C;
const exact: "dark" = c.mode;
console.log(exact);