YUI Library Examples: Menu Family: Adding A Context Menu To A Table

When adding context menus to large data structures like a <table> or large list (<ol> or <ul>), it is recommended to bind a single YAHOO.widget.ContextMenu instance to the structure's root element, than to a set of its child nodes (<tr>s or <li>s). Doing so significantly improves the performance of a web page or application by reducing the number of "contextmenu" event handlers as well as the number of YAHOO.widget.ContextMenu instances in memory.

Begin, by creating an <table> and giving <tr> elements that should have the same context menu a similar class name.

Next, create an object literal that maps each class name to a set of MenuItem configuration properties.

/*
    Map of CSS class names to arrays of MenuItem 
    configuration properties.
*/

var oContextMenuItems = {

"type1": [
                "Context Menu 1, Item 1", 
                {
                    text: "Context Menu 1, Item 2", 
                    submenu: { 
                                id: "submenu1", 
                                lazyload: true, 
                                itemdata: [
                                    "Context Menu 1 Submenu, Item 1", 
                                    "Context Menu 1 Submenu, Item 2", 
                                    "Context Menu 1 Submenu, Item 3", 
                                    "Context Menu 1 Submenu, Item 4"
                                ] 
                            } 
                }, 
                "Context Menu 1, Item 3", 
                "Context Menu 1, Item 4"
            ],

"type2": [
                "Context Menu 2, Item 1", 
                "Context Menu 2, Item 2", 
                "Context Menu 2, Item 3", 
                "Context Menu 2, Item 4", 
                "Context Menu 2, Item 5", 
                "Context Menu 2, Item 6", 
                "Context Menu 2, Item 7", 
                "Context Menu 2, Item 8", 
                "Context Menu 2, Item 9", 
                "Context Menu 2, Item 10"
            ],

"type3": [
                "Context Menu 3, Item 1", 
                "Context Menu 3, Item 2", 
                "Context Menu 3, Item 3", 
                "Context Menu 3, Item 4"
            ],

"type4": [
                "Context Menu 4, Item 1", 
                "Context Menu 4, Item 2"
            ],

"type5": [
                "Context Menu 5, Item 1", 
                "Context Menu 5, Item 2", 
                "Context Menu 5, Item 3", 
                "Context Menu 5, Item 4", 
                "Context Menu 5, Item 5", 
                "Context Menu 5, Item 6"
            ]

};

Use the onContentReady method of the Event utility to instantiate the ContextMenu as soon as the elements whose "contextmenu" event trigger its display are ready to be scripted.

Lastly, add a "beforeShow" event handler to the ContextMenu instance. This event handler makes use of the "contextEventTarget" property to determine which <tr> element was the target of the "contextmenu" event. Once found, the <tr> element's class name is used to look up its corresponding menu items in the "oContextMenuItems" map, which are then added to the ContextMenu instance via the "addItems" method.

/*
     Initialize the ContextMenu instance when the the elements 
     that trigger their display are ready to be scripted.
*/

YAHOO.util.Event.onContentReady("dataset", function () {

/*
         Utility function used to return the parent <tr> element of
         the actual node in the "dataset" table that fired the 
         "contextmenu" event.
    */

function getTableRowFromEventTarget(p_oNode) {

if (p_oNode.tagName.toUpperCase() == "TR") {
        
            return p_oNode;

}
        else {

/*
                 If the target of the event was a child of a TR, 
                 get the parent TR element
            */

do {

if (p_oNode.tagName.toUpperCase() == "TR") {

return p_oNode;

break;
                
                }

}
            while ((p_oNode = p_oNode.parentNode));
        
        }
    
    }

var oSelectedTR;    // The currently selected TR

/*
         "beforeshow" event handler for the ContextMenu instance - 
         replaces the content of the ContextMenu instance based 
         on the CSS class name of the <tr> element that triggered
         its display.
    */

function onContextMenuBeforeShow(p_sType, p_aArgs) {

var aMenuItems,
            aClasses;

if (this.getRoot() == this) {

/*
                 Get the <tr> that was the target of the 
                 "contextmenu" event.
            */

oSelectedTR = getTableRowFromEventTarget(this.contextEventTarget);

/*
                Get the array of MenuItems for the CSS class name from 
                the "oContextMenuItems" map.
            */

if (YAHOO.util.Dom.hasClass(oSelectedTR, "odd")) {

aClasses = oSelectedTR.className.split(" ");

aMenuItems = oContextMenuItems[aClasses[0]];
            
            }
            else {
                
                aMenuItems = oContextMenuItems[oSelectedTR.className.trim()];

}

// Remove the existing content from the ContentMenu instance

this.clearContent();

// Add the new set of items to the ContentMenu instance                    
            
            this.addItems(aMenuItems);

// Render the ContextMenu instance with the new content

this.render();

/*
                 Highlight the <tr> element in the table that was 
                 the target of the "contextmenu" event.
            */

YAHOO.util.Dom.addClass(oSelectedTR, "selected");
        
        }
        
    }

/*
         "hide" event handler for the ContextMenu - used to 
         clear the selected <tr> element in the table.
    */

function onContextMenuHide(p_sType, p_aArgs) {

if (this.getRoot() == this && oSelectedTR) {

YAHOO.util.Dom.removeClass(oSelectedTR, "selected");
        
        }
    
    }

/*
         Instantiate a ContextMenu:  The first argument passed to 
         the constructor is the id of the element to be created; the 
         second is an object literal of configuration properties.
    */

var oContextMenu = new YAHOO.widget.ContextMenu("contextmenu", { 
                                                            trigger: "dataset", 
                                                            lazyload: true 
                                                            });

/*
         Subscribe to the ContextMenu instance's "beforeshow" and 
         "hide" events.
    */

oContextMenu.subscribe("beforeShow", onContextMenuBeforeShow);
    oContextMenu.subscribe("hide", onContextMenuHide);

});

YUI Library Examples: Menu Family: Adding A Context Menu To A Table

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