koa-connect/index.js

Use Connect/Express middleware in Koa

"use strict";
const noop = () => { };
/**
 * If the middleware function does not declare receiving the `next` callback
 * assume that it's synchronous and invoke `next` ourselves.
 */
function noCallbackHandler(ctx, connectMiddleware, next) {
    connectMiddleware(ctx.req, ctx.res, noop);
    return next();
}
/**
 * The middleware function does include the `next` callback so only resolve
 * the Promise when it's called. If it's never called, the middleware stack
 * completion will stall.
 */
function withCallbackHandler(ctx, connectMiddleware, next) {
    return new Promise((resolve, reject) => {
        connectMiddleware(ctx.req, ctx.res, (err) => {
            if (err)
                reject(err);
            else
                resolve(next());
        });
    });
}
/**
 * Returns a Koa middleware function that varies its async logic based on if the
 * given middleware function declares at least 3 parameters, i.e. includes
 * the `next` callback function.
 */
function koaConnect(connectMiddleware) {
    const handler = connectMiddleware.length < 3 ? noCallbackHandler : withCallbackHandler;
    return function koaConnect(ctx, next) {
        return handler(ctx, connectMiddleware, next);
    };
}
module.exports = koaConnect;