See the whole code

	/* Any JavaScript here will be loaded for all users on every page load. */
	/* https://www.mediawiki.org/wiki/Extension:WikiEditor/Toolbar_customization */
	/* Example stuff can be seen in the /extentions/WikiEditor/modules/jquery.wikiEditor.dialogs.config.js */
	/*the code partly originated form https://www.mediawiki.org/wiki/Extension:WikiEditor/Toolbar_customization and the /extentions/WikiEditor/modules/jquery.wikiEditor.dialogs.config.js */
	var customizeToolbar = function() {
		$.wikiEditor.modules.dialogs.modules['insert-mytool'] ={
					titleMsg: 'wikieditor-toolbar-tool-mytool-title',
					id: 'wikieditor-toolbar-mytool-dialog',
					html: '\
						<fieldset>\
							<div class="wikieditor-toolbar-field-wrapper">\
								<label for="wikieditor-toolbar-file-target" rel="wikieditor-toolbar-file-target" id="wikieditor-toolbar-tool-file-target-label"></label>\
								<input type="text" id="wikieditor-toolbar-file-target"/>\
							</div>\
							<div class="wikieditor-toolbar-field-wrapper">\
								<label for="wikieditor-toolbar-file-caption" rel="wikieditor-toolbar-file-caption"></label>\
								<input type="text" id="wikieditor-toolbar-file-caption"/>\
							</div>\
							<div class="wikieditor-toolbar-file-options">\
								<div class="wikieditor-toolbar-field-wrapper">\
									<label for="wikieditor-toolbar-file-size" rel="wikieditor-toolbar-file-size"></label><br/>\
									<input type="text" id="wikieditor-toolbar-file-size" size="5"/>\
								</div>\
								<div class="wikieditor-toolbar-field-wrapper">\
									<label for="wikieditor-toolbar-file-float" rel="wikieditor-toolbar-file-float"></label><br/>\
									<select type="text" id="wikieditor-toolbar-file-float">\
									<option value="default" selected="selected" rel="wikieditor-toolbar-file-default"></option>\
									<option data-i18n-magic="img_none"></option>\
									<option data-i18n-magic="img_center"></option>\
									<option data-i18n-magic="img_left"></option>\
									<option data-i18n-magic="img_right"></option>\
									</select>\
								</div>\
								<div class="wikieditor-toolbar-field-wrapper">\
									<label for="wikieditor-toolbar-file-format" rel="wikieditor-toolbar-file-format"></label><br/>\
									<select type="text" id="wikieditor-toolbar-file-format">\
									<option selected="selected" data-i18n-magic="img_thumbnail">thumb</option>\
									<option data-i18n-magic="img_framed"></option>\
									<option data-i18n-magic="img_frameless"></option>\
									<option value="default" rel="wikieditor-toolbar-file-format-none"></option>\
									</select>\
								</div>\
							</div>\
						</fieldset>',
					init: function () {
	window.alert("hi!")
					},
					dialog: {
						resizable: false,
						dialogClass: 'wikiEditor-toolbar-dialog',
						width: 590,
						buttons: {
							'wikieditor-toolbar-tool-mytool-insert': function () {
								var fileName, caption, fileFloat, fileFormat, fileSize, fileTitle,
									options, fileUse,
									hasPxRgx = /.+px$/;
								fileName = $( '#wikieditor-toolbar-file-target' ).val();
								caption = $( '#wikieditor-toolbar-file-caption' ).val();
								fileFloat = $( '#wikieditor-toolbar-file-float' ).val();
								fileFormat = $( '#wikieditor-toolbar-file-format' ).val();
								fileSize = $( '#wikieditor-toolbar-file-size' ).val();
								// Append px to end to size if not already contains it
								if ( fileSize !== '' && !hasPxRgx.test( fileSize ) ) {
									fileSize += 'px';
								}
								if ( fileName !== '' ) {
									fileTitle = new mw.Title( fileName );
									// Append file namespace prefix to filename if not already contains it
									if ( fileTitle.getNamespaceId() !== 6 ){
										fileTitle = new mw.Title( fileName, 6 );
									}
									fileName = fileTitle.toText();
								}
								options = [ fileSize, fileFormat, fileFloat ];
								// Filter empty values
								options = $.grep( options, function ( val ) {
									return val.length && val !== 'default';
								} );
								if ( caption.length ) {
									options.push( caption );
								}
								fileUse = options.length === 0 ? fileName : ( fileName + '|' + options.join( '|' ) );
								$( this ).dialog( 'close' );
								$.wikiEditor.modules.toolbar.fn.doAction(
									$( this ).data( 'context' ),
									{
										type: 'replace',
										options: {
											pre: '[[',
											peri: fileUse,
											post: ']]',
											ownline: true
										}
									},
									$( this )
								);

								// Restore form state
								$( ['#wikieditor-toolbar-file-target',
									'#wikieditor-toolbar-file-caption',
									'#wikieditor-toolbar-file-size',
									'#wikieditor-toolbar-file-float',
									'#wikieditor-toolbar-file-format'].join( ',' )
								).val( '' );
							},
							'wikieditor-toolbar-tool-mytool-cancel': function () {
								$( this ).dialog( 'close' );
							}
						},
						open: function () {
							$( '#wikieditor-toolbar-file-target' ).focus();
							if ( !( $( this ).data( 'dialogkeypressset' ) ) ) {
								$( this ).data( 'dialogkeypressset', true );
								// Execute the action associated with the first button
								// when the user presses Enter
								$( this ).closest( '.ui-dialog' ).keypress( function( e ) {
									if ( e.which === 13 ) {
										var button = $( this ).data( 'dialogaction' ) ||
											$( this ).find( 'button:first' );
										button.click();
										e.preventDefault();
									}
								});

								// Make tabbing to a button and pressing
								// Enter do what people expect
								$( this ).closest( '.ui-dialog' ).find( 'button' ).focus( function() {
									$( this ).closest( '.ui-dialog' ).data( 'dialogaction', this );
								});
							}
						}
					}
				}


		//a test addition. It does add a :) in order to make discussions in tough editwars way nicer.
		 $( '#wpTextbox1' ).wikiEditor('addToToolbar',{
			 'section': 'main',
			 'group': 'insert',
			 'tools': {
			          'smile': {
			                  label: 'Smile!', // or use labelMsg for a localized label, see above
			                  type: 'button',
			                  icon: '//upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Gnome-face-smile.svg/22px-Gnome-face-smile.svg.png',
			                  action: {
			                          type: 'encapsulate',
			                          options: {
			                                  pre: ":)" // text to be inserted
			                          }    
			                  }
			          }
			  }
			  
			  
	 });//END:wikiEditor('addToToolbar
	 
	 
	 $( '#wpTextbox1' ).wikiEditor( 'addToToolbar', {
			 'section': 'main',
			 'group': 'insert',
			 'tools': {
			          'mytool': {
			                  'label': 'mytool', // or use labelMsg for a localized label, see above
			                  'type': 'button',
			                  'icon': 'http://upload.wikimedia.org/wikipedia/commons/4/49/Tango_-_text-x-script_22px.png',
			                  'action': {
			 							'type': 'dialog',
										'module':'insert-mytool'
				 					}
			          }
			  }
			  
			  
	 });//END:wikiEditor('addToToolbar
	};







	//loader
	if ( $.inArray( mw.config.get( 'wgAction' ), ['edit', 'submit'] ) !== -1 ) {
			  mw.loader.using( 'user.options', function () {
			          if ( mw.user.options.get('usebetatoolbar') ) {
			                  mw.loader.using( 'ext.wikiEditor.toolbar', function () {
			                          $(document).ready( customizeToolbar );
			                  } );
			          }
			  } );
	}`