显示Express中每个请求的日志时间？

Question

I've some problem in here. I don't know why this is happened. I put timestamps code with Moment.js library, not only with that library, recently i created manually for showing timestamps but when i send request, time not updated. I put datetime in my file route. But this is work in server file.

So for example

server.js

var express = require('express')
var app = express()
var moment = require('moment')

app.use(function(req, res, next){
  console.log(moment().format('HH:mm:ss') + ' From server.js') //Showing time now
  next();
  })

app.use('/', index)
app.listen(8001)

routes/index.js

var express = require('express')
var app = express()
var router = express.Router()
var moment = require('moment')
var timestamps = moment().format('HH:mm:ss')

router.get('/', function(req, res){
  console.log(timestamps + ' From routes/index.js')
})

module.exports = routes

And i begin test for my code for first time GET localhost:8001/

My system time showing 16:20:51

[nodemon] 1.11.0
[nodemon] to restart at any time, enter `rs`
[nodemon] watching: *.*
[nodemon] starting `node ./bin/www`
16:20:51 From Server.js
16:20:51 From routes/index.js

And the second request my system time showing 16:22:52

[nodemon] 1.11.0
[nodemon] to restart at any time, enter `rs`
[nodemon] watching: *.*
[nodemon] starting `node ./bin/www`
16:22:52 From Server.js
16:20:51 From routes/index.js

Nah, the second request still get existing time log from first request, this is only happened in routes. But work with well in server.js

Is it happened because variable timestamps outside function? But when i running without variable, it's worked.

router.get('/', function(req, res){
  console.log(moment().format('HH:mm:ss') + ' From routes/index.js')
})

Why this is can be happened? Thanks

Answer 1

You cache the timestamp value.

Modify your route file this way:

var express = require('express')
var app = express()
var router = express.Router()
var moment = require('moment')

router.get('/', function(req, res){
  var timestamps = moment().format('HH:mm:ss')
  console.log(timestamps + ' From routes/index.js')
})

module.exports = routes

You have to understand that file is included once the application started and until it is running. The only part is called from time to time here is the function handler of the route:

function(req, res){
  var timestamps = moment().format('HH:mm:ss')
  console.log(timestamps + ' From routes/index.js')
}

Answer 2

You were on right track! It is because you define timestamps outside the middleware*. The middleware is the function you register to the route and it gets called on each request that matches the specified url. So when you invoke moment() inside the middleware it returns the actual date and time of the request, since this function is executed only during the procession of a request. While in your case the code with the timestamps defined outside the function is executed only once - at the startup of the application when you require routes/index.js . But you may still use variable, just define it on the right place:

var express = require('express')
var app = express()
var router = express.Router()
var moment = require('moment')
var format = 'HH:mm:ss';

router.get('/', function(req, res){
  var timestamps = moment().format(format)
  console.log(timestamps + ' From routes/index.js')
})

module.exports = routes