Is there a connection to database on server by javascribt?

no its used for interface just..

A better way to connect to a sql server would be to use some server side language like PHP, Java, .NET, among others. Client javascript should be used only for the interfaces.

No. JavaScript is aclient side script

JavaScript isn't only a front side language in years.

You can use Javascript with NodeJS on server Side to connect to your database and you'll have better performance than with Java, php or .net languages.

Some npm modules exists for connect to database. (ex: mssql for MS SQL Server database) (https://www.npmjs.com/package/mssql). mongodb & mongoose for a connection to a nosql mongoDB database.