node.js - express res.send as result of promise -

i'm not understanding what's going on...

using q promises, works:

const deferred = q.defer(); deferred.resolve('hellow');  const mypromise = deferred.promise;  router.get('/items', (req, res) => {     mypromise.then((result) => res.send(result)); }); 

but doesn't, keeps browser if request never ends:

router.get('/items', (req, res) => {     mypromise.then(res.send); }); 

what's wrong?

below fragment of express library related res.send:

res.send = function send(body) {     var chunk = body;     var encoding;     var len;     var req = this.req;     var type;      // settings     var app = this.app;      // allow status / body     if (arguments.length === 2) {         // res.send(body, status) backwards compat         if (typeof arguments[0] !== 'number' && typeof arguments[1] === 'number') {             deprecate('res.send(body, status): use res.status(status).send(body) instead');             this.statuscode = arguments[1];         } else {             deprecate('res.send(status, body): use res.status(status).send(body) instead');             this.statuscode = arguments[0];             chunk = arguments[1];         }     }  //..... 

as can see, there lots of this references. in case mypromise.then(res.send) this refers promise object, not res, that's why code doesn't work.

you can change context using .bind method, this refer res object:

router.get('/items', (req, res) => {     mypromise.then(res.send.bind(res)); });