This project is part of the @thi.ng/umbrella monorepo.
Dynamically scoped variable bindings.
References:
ALPHA - bleeding edge / work-in-progress
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yarn add @thi.ng/dynvarES module import:
<script type="module" src="https://cdn.skypack.dev/@thi.ng/dynvar"></script>For Node.js REPL:
# with flag only for < v16
node --experimental-repl-await
> const dynvar = await import("@thi.ng/dynvar");
Package sizes (gzipped, pre-treeshake): ESM: 301 bytes
TODO - See tests for usage...
import { dynvar } from "@thi.ng/dynvar";
import { appendFileSync } from "fs";
interface Logger {
log(...args: any[]): void;
}
// create dynamically scoped variable
// set default/root binding
const logger = dynvar<Logger>(console);
// dummy function using `logger`
const foo = () => {
// deref() returns var's current value
logger.deref().log("begin foo...");
for (let i = 0; i < 5; i++) {
logger.deref().log(i);
}
logger.deref().log("foo done.");
};
foo();
// (output in console)
// begin foo...
// 0
// 1
// 2
// 3
// 4
// foo done.
// Alternative Logger impl
class FileLogger implements Logger {
constructor(protected path: string) {}
log(...args: any[]) {
appendFileSync(this.path, args.join(", ") + "\n");
}
}
// re-execute `foo` with temporary dynamic scope in which
// logger is bound to given new value (i.e. here file logger)
logger.withBinding(new FileLogger("./foo.txt"), foo);
// old scope again (back to using console)
logger.deref().log("good bye");
// "good bye"Display log file contents:
cat foo.txt
# begin foo...
# 0
# 1
# 2
# 3
# 4
# foo done.Karsten Schmidt
If this project contributes to an academic publication, please cite it as:
@misc{thing-dynvar,
title = "@thi.ng/dynvar",
author = "Karsten Schmidt",
note = "https://thi.ng/dynvar",
year = 2016
}© 2016 - 2022 Karsten Schmidt // Apache Software License 2.0