public static function getUserId($username)
{
    $db = JFactory::getDbo();
    $query = $db->getQuery(true)
        ->select($db->quoteName('id'))
        ->from($db->quoteName('#__users'))
        ->where($db->quoteName('username') . ' = ' . $db->quote($username));
    $db->setQuery($query, 0, 1);

    return $db->loadResult();
}

And you can use JUserHelper:

$username = 'admin';
$userId    = JUserHelper::getUserId($username);

echo $userId;

Launch Terminal and be in the home directory to get started:

• Using emacs, nano, vi, or whatever your favorite text editor is to edit .inputrc, we’ll use nano for the walkthrough:

nano .inputrc

• Paste in the following three rules on unique lines:

set completion-ignore-case on
set show-all-if-ambiguous on
TAB: menu-complete

• Hit Control+O to save changes to .inputrc followed by control+X to quit
• Open a new Terminal window or tab, or type “login” to open a new session with the rules in effect
• Start typing a command, path, or something else and hit the Tab key to see the improvements firsthand

How use keyboard events? It's simple:

<script>
    	$(document).ready(function() {
	  		$(window).keydown(function(event){
	    		if(event.keyCode == 13) {
	      			event.preventDefault();
	      			return false;
	    		}
	 		 });
		});
    
</script>

Enlarging the Icons
Let's say you want to change the grid size to four rows by four columns of app icons , which will make for significantly bigger icons. Open a Terminal window (open Finder, select the Applications list, and then in the list of applications double-click Terminal within the Utilities folder), and type the following two lines, the first of which refers to the number of icon rows and the second of which refers to the number of icon columns:

defaults write com.apple.dock springboard-rows -int 4
defaults write com.apple.dock springboard-columns -int 4;killall Dock

Then activate Launchpad to see the changes

Shrinking the Icons
To make the icons smaller, we simply increase the grid size. Increasing the grid size to 10x10 icons will shrink the icons significantly into a compact layout but still leave them usable. It can be done as follows by typing these two lines into a Terminal window:

defaults write com.apple.dock springboard-rows -int 6
defaults write com.apple.dock springboard-columns -int 12;killall Dock