JAVASCRIPT

document middleware in express

//4 types of middleware document,query,aggregate and model 
//document middleware run before .save() and .create()
const slugify = require('slugify')

tourSchema.pre('save',function(next) {
     console.log('will save document')
     this.slug= slugify(this.name,{lower:true})
     next()
})

what is middleware in express js

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

var myLogger = function (req, res, next) {
  console.log('LOGGED')
  next()
}

app.use(myLogger)

app.get('/', function (req, res) {
  res.send('Hello World!')
})

what is middleware in express js

const requestLogger = (request, response, next) => {
  console.log('Method:', request.method)
  console.log('Path:  ', request.path)
  console.log('Body:  ', request.body)
  console.log('---')
  next()
}

middleware in express

1)Express app receives a request when someone hits a server for which it will create
request and response.
2)middleware is used to manipulate request.
3)It is middleware because it is a function that run between request and response cycle.
4) middleware stack. middleware that appear first will run first.
5)middleware is like pipeline which end with response object.
//Creating own middleware
//this middleware apply to each and every request
//so,  if we put in last then it will not work.
app.use((req,res,next)=> {
     console.log('Hello from middleware')
     next() 
})
//adding request time 
app.use((req,res,next)=> {
     req.requestTime= new Date().toISOString() //this is method and we need to call that
     next()
})

middleware in express

app.use('/user/:id', (req, res, next) => {
  console.log('Request Type:', req.method)
  next()
})

Express Middleware

const express = require('express');
const app = express();

function middlewareFunction(request, response, next){
  ...
  next()
}

app.use(middlewareFunction)