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disposable: wrapper to make an object disposable with the using keyword

using feature explanation in TypeScript 5.2 docs

Example:

Create val
import { disposable } from "https://esm.town/v/postpostscript/disposable";

using state = disposable(
  {
    x: 1,
    y: 2,
  },
  (value) => console.log("state disposed", value),
);
// state disposed { x: 1, y: 2, [Symbol(Symbol.dispose)]: [Function (anonymous)] }

or, to use a proxy instead of modifying the original object:

Create val
using state = disposable(
  {
    x: 1,
    y: 2,
  },
  (value) => console.log("proxyState disposed", value),
  true,
);
// proxyState disposed { x: 1, y: 2 }

Full Example

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export function disposable<T extends object>(
value: T,
onDispose: (value: T) => void,
proxy = false,
): T {
const dispose = async () => {
if (proxy && value[Symbol.dispose]) {
await value[Symbol.dispose]();
}
return onDispose(value);
};
if (!proxy) {
value[Symbol.dispose] = dispose;
return value;
}
return new Proxy(value, {
get(target, key, receiver) {
if (key === Symbol.dispose) {
return dispose;
}
return Reflect.get(target, key, receiver);
},
});
}
April 24, 2024