Thursday, April 4, 2019

How To Sort Array By Name Or Date In Javascript?

Suppose you have an array users. You need to sort the array by name or date.
var users = [
  {id: 1, firstName: 'Anup', created_date: Mar 12 2012 10:00:00 AM}, 
  {id: 2, firstName: 'Tom', created_date: Mar 8 2012 08:00:00 AM}
];
To sort the array of objects by created_date
Turn your strings into dates, and then subtract them to get a value that is either negative, positive, or zero.
Example:
 users.sort((a, b) => new Date(b.created_date) - new Date(a.created_date));   
To sort the array of objects by firstName
Suppose you have an array users. You may use users.sort and pass a function that takes two arguments and compare them (comparator).
It should return
• something negative if first argument is less than second (should be placed before the second in resulting array)
• something positive if first argument is greater (should be placed after second one)
• 0 if those two elements are equal.

In our case if two elements are a and b, we want to compare a.firstname and b.firstname. When sorting strings toLowerCase() is very important - capital letters could affect your sort.
Example:
users.sort((a, b) => a.firstName.toLowerCase() !== b.firstName.toLowerCase() ? a.firstName.toLowerCase() < b.firstName.toLowerCase() ? -1 : 1 : 0);
If compared strings contain unicode characters you can use localeCompare function of String class like the following:
users.sort((a, b) => a.firstname.toLowerCase().localeCompare(b.firstname.toLowerCase()));

Monday, April 1, 2019

How To Solve Mongo - couldn't connect to server 127.0.0.1:27017 error?

Problem:
[js] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed: SocketException: Error connecting to 127.0.0.1:27017 :: caused by :: Connection refused :
connect@src/mongo/shell/mongo.js:257:13
@(connect):1:6

Solution
Normally this caused because you didn't start mongod process before you try starting mongo shell.

Start mongod server
 mongod
Open another terminal window and start mongo shell
 mongo