ctx-hook


Overview

ctx-hook is a TypeScript library that uses Node.js's asynchronous context tracking to enable property hooking that activates only within the asynchronous contexts of wrapper functions created by its API.

Example

``typescript
import { useGlobalCtxHook, useCtxHook } from 'ctx-hook'

// Create a context hook for global.Date to travel to 1 day ago.
const { wrap, dispose } = useGlobalCtxHook('Date', Date0 => {
const getTravelledNow = () => Date0.now() - 864e5
const getTravelledDate = () => new Date0(getTravelledNow())
const Date1 = new Proxy(Date0, {
construct(_, args) {
if (! args.length) return getTravelledDate()
return new Date0(...args as [])
},
apply() {
return getTravelledDate().toString()
},
get(_, prop: keyof DateConstructor) {
if (prop === 'now') return getTravelledNow
return Date0[prop]
}
})
return Date1
})

// Define a function that outputs the current time twice.
const fn = async () => {
console.log(Date.now())
await new Promise(resolve => setTimeout(resolve, 0))
console.log(Date.now())
}

// Wrap the function so that all access (sync or async) to Date will be hooked.
const fnTravelled = wrap(fn)

fnTravelled()

// Dispose the context hook to restore the original Date.
dispose()
``