@beaker73/async-context v0.1.2

AsyncContext

Provides a context over async function calls. Much like AsyncLocalStorage on node.js, but for browsers.

Important Warning

The way this is done is slightly hacky and might not work on all browsers. We generate a random id that is injected into the stack-trace by calling a function containing the id in a part of the name as a marker.

The implementation is dependent on the way the browser generates the stack traces and thus is not guaranteed to work as stack traces are not part of any standard.

Usage

// define some context that should be available anywhere
const context = { value: "banana" };

// call a function with the context.
// even after context switches 
const result = await callWithContext(context, async () => {
	
	// get the context
	const c1 = getContext();
	
	await someAsync();
	
	// stil get the same context
	const c2 = getContext();

	// maybe return a result
	return "coconut";

	async function someAsync() {
		await new Promise(resolve => setTimeout(resolve, 5000));
		
		// also the same context
		const c3 = getContext();
	}
})

Functions

callWithContext

Calls a function and set a context during the whole execution of that context. Even during async awaits with context switches. As soon as code continues after the await, the getContext will return the correct context again.

callWithContext<
	// type arguments
	Context = unknown, 
	Result = void
>(
	// arguments
	func: () => Promise<Result>
	context: Context
)
	// result
	: Promise<Result>;

type arguments

arguments

result

getContext

Gets the context at the current execution point. If the code was not started via callWithContext the function throws.

getContext<
	// type arguments
	Context = unknown
>()
	// result
	: Context

type arguments

result

throws

tryGetContext

Tryies the context at the current execution point. If the code was not started via callWithContext the function returns undefined instead.

result