Using an array of callback functions in express in typescript

Question

I'm trying to re-create the express routing example in typescript

I have...

/// <reference path='Scripts/typings/express/express.d.ts' />
import express = require('express');
var app = express();

var cb0: express.RequestHandler = function (req, res, next) {
    console.log('CB0');
   next();
}

var cb1: express.RequestHandler = function (req, res, next) {
    console.log('CB1');
    next();
}

var cb2: express.RequestHandler = function (req, res) {
    res.send('Hello from C!');
}

var arr: express.RequestHandler[] = [cb0, cb1, cb2];

app.get('/example/c', arr);

The first error the typescript compiler throws at me is for '/example/c' saying Argument of type 'string' is not assignable to parameter of type 'RegExp'... odd, since in express.d.ts the function is defined as allowing a string, or a regex... but, ok, I change it to new RegExp('/example/c')

Then it throws the error Argument of type 'RequestHandler[]' is not assignable to parameter of type 'RequestHandler'. at me. Also odd, since the express.d.ts file has the method defined as allowing an array.

Very new to typescript here, and these are some cryptic error messages...

Probably worth noting, the express.d.ts came from DefinitelyTyped -github.com/borisyankov/DefinitelyTyped/blob/master/express/… — TranquilMarmot
– TranquilMarmot, Commented May 2, 2015 at 7:19

Rajeev Goel · Accepted Answer · 2015-05-02 07:53:47Z

2

Change the last line of your snippet to this, and you should be fine:

app.get('/example/c', cb0, cb1, cb2);

You can't pass in an array of RequestHandlers to that second parameter .... it is a special type of parameter in Typescript called "rest" parameter, analogous to "params" in C#.

answered May 2, 2015 at 7:53

Rajeev Goel

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1 Comment

TranquilMarmot Over a year ago

Thank you! That makes a lot of sense.

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