getting empty array on express response

Question

I am working on an example, I am trying to get a single employee instance from this express example, but when I type, localhost:3000/1, I am getting an empty array. does anyone know what I am doing wrong here?

'use strict';

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

var employees = [
	{
   "EmployeeID" :1 ,
   "EmployeeName" : "RNA Team",
   "Salary" : "200000",
   "Address" : "Bangalore"
   },
   {
   "EmployeeID" :2 ,
   "EmployeeName" : "Mahesh Samabesh",
   "Salary" : "100000",
   "Address" : "Hydrabad"
   },
   {
   "EmployeeID" :3 ,
   "EmployeeName" : "Rui Figo",
   "Salary" : "50000",
   "Address" : "Dallas"
   },
   {
   "EmployeeID" :4 ,
   "EmployeeName" : "Indradev Jana",
   "Salary" : "456789",
   "Address" : "Los Angles"
   },
   {
   "EmployeeID" :5 ,
   "EmployeeName" : "Suresh Shailesh",
   "Salary" : "1234567",
   "Address" : "Patna"
  }
];

//Get the employees records

app.get('/', function(req, res){
	res.send(employees);
});

//run the server
var server = app.listen(3000, function(){
	var host = server.address().address;
	var port  = server.address().port;

	console.log('Server started and listening at:> http://%s:%s', host, port);
});

//Get single employee record
app.get('/:EmployeeID', function(req, res){
	var employeeID = req.params.EmployeeID;

	//Get Employee Records whose EmployeeID = get the EmployeeID at runtime
	var filteredEmployee = [];

	for(var i=0; i < employees.length; i++){
		if(employees[i].EmployeeID == employeeID){
			filteredEmployee.push(employees[i]);
		}
	} //end Loop
	employees = filteredEmployee;
	console.log(filteredEmployee);
	res.send(employees);
});

What is req.params.EmployeeID when you try it? One possibility here is that you aren't passing in the right ID so thus you never find a match. Also, you should not be changing the employees array just because you're searching it. That will damage the data for the next time you want to search it. — jfriend00
– jfriend00, Commented Feb 19, 2017 at 18:29

Balázs Édes · Accepted Answer · 2017-02-19 18:26:42Z

2

You really shouldn't mutate your data in a query operation. You could do something like this:

app.get('/:EmployeeID', (req, res) => {
  const employeeID = req.params.EmployeeID;
  // filter the employees without mutating the array, and get the first result
  const [employee] = employees.filter(e => e.EmployeeID === employeeID)
  // if there was a result, send it, otherwise send an error
  res.json(employee ? employee : { error: `Employee with id ${employeeID} not found` })
});

answered Feb 19, 2017 at 18:26

Balázs Édes

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1 Comment

Lucky500 Over a year ago

Thanks Balazs, I tried to get this to work, but not sure, what I did wrong here. Am I able to set an array as a const in ES5? or that is just a placeholder?

CWright · Accepted Answer · 2017-02-19 18:38:26Z

You're re-assigning your employees object.

employees = filteredEmployee;

will set your employees object to be the single found employee. So it will work the first time, and it does. Then any subsequent tries it will only have a single employee in it.

You just want to do res.send(filteredEmployee) after your loop.

also your code is picking up your browsers request to /favicon.ico as an employee param.

adding this will block that:

 app.get('/favicon.ico', function(req, res) {
     res.send(204);
 });

Fixed example:

'use strict';

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

var employees = [
    {
   "EmployeeID" :1 ,
   "EmployeeName" : "RNA Team",
   "Salary" : "200000",
   "Address" : "Bangalore"
   },
   {
   "EmployeeID" :2 ,
   "EmployeeName" : "Mahesh Samabesh",
   "Salary" : "100000",
   "Address" : "Hydrabad"
   },
   {
   "EmployeeID" :3 ,
   "EmployeeName" : "Rui Figo",
   "Salary" : "50000",
   "Address" : "Dallas"
   },
   {
   "EmployeeID" :4 ,
   "EmployeeName" : "Indradev Jana",
   "Salary" : "456789",
   "Address" : "Los Angles"
   },
   {
   "EmployeeID" :5 ,
   "EmployeeName" : "Suresh Shailesh",
   "Salary" : "1234567",
   "Address" : "Patna"
  }
];

//Get the employees records

app.get('/', function(req, res){
    res.send(employees);
});

//run the server
var server = app.listen(3000, function(){
    var host = server.address().address;
    var port  = server.address().port;

    console.log('Server started and listening at:> http://%s:%s', host, port);
});

app.get('/favicon.ico', function(req, res) {
    res.send(204);
});

//Get single employee record
app.get('/:employeeID', function(req, res){
    var employeeID = req.params.employeeID;

    //Get Employee Records whose EmployeeID = get the EmployeeID at runtime
    var filteredEmployee = [];

    for(var i=0; i < employees.length; i++){
        if(employees[i].EmployeeID == employeeID){
            filteredEmployee.push(employees[i]);
        }
    } //end Loop
    console.log(filteredEmployee);
    res.send(filteredEmployee);
});

Prakash Sharma · Accepted Answer · 2017-02-19 18:35:10Z

1

You are actually mutating your data. The way you are doing will work only for once and then your employee array will change. So just remove employees = filteredEmployee; and directly send res.send(filteredEmployee); instead.

edited Feb 19, 2017 at 18:35

answered Feb 19, 2017 at 18:29

Prakash Sharma

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1 Comment

jfriend00 Over a year ago

Why would this fix anything?

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