🔙 Backend Support

LiTScript supports now building server-side (backend) JS modules. These are Express.js applications which the LiTScript development server loads, and reloads when its source changes. In a standalone deployment scenario, you include the built module in a node.js application. An example backend module can be found in tests/test-backend.ts.

import * as exp from 'express'

Express Middleware

The backend API is implemented as an Express middleware. We load the bundle dynamically and invalidate it whenever it's updated.

The full path to the bundled JS module is stored here. The bundler sets this variable using the setBackendBundle function. The reference to the Express app is initially not set.

let bundle: string
let app: exp.Application | undefined

export function setBackendBundle(path: string) {
    bundle = path
}

This is the middleware that the development server uses to hanlde requests to backend. The backend is a bundled JS file whose default export should return an Express Application object.

export function backend(req: exp.Request, res: exp.Response, 
    next: exp.NextFunction) {
    if (!bundle)
        next()
    if (!app)
        app = require(bundle).default
    app?.(req, res, next)
}

Invalidate the backend module after it has changed. Unset the app reference and remove the bundle from Node.js require cache.

export function invalidateBackend() {
    if (app) {
        app = undefined
        delete require.cache[bundle] 
    }
}