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javascriptjqueryprototypejs

Best way to implement .lastChild using Prototype or jQuery

Currently we are using prototype and jQuery as our js frameworks. Right now, jQuery is set to $j() to prevent conflicts from prototype.

In the past, we've used a lot of prototype's Element.down(), Element.next(), and Element.previous() to traverse the DOM. However, I need a simple way to retrieve the last child element. I know i can loop through an array by using Element.childElements() but I would like something inline that reads cleanly and can be pipelined.

Just thought I would ask before I go reinventing the wheel. Here's a snippet of code that has lastChild in it that needs to be replaced:

_find : function(rows, address) {
        var obj = null;
        for (var i=0; i < rows.length && obj == null; i++) {
            if (rows[i].down().className == 'b')
                obj = this._find(rows[i].lastChild.down().down().childElements(), address);
            else if (rows[i].lastChild.getAttribute('tabAddress') == address)
                return rows[i].lastChild;
        }
        return obj;
    }
Solution

  • Guys, note that the selector functions return arrays of elements (not single elements), so you must adddress the element in the result array by index: [0].

    Code in prototype

    //if you only have the id of the parent
var lastChild = $$("#parent :last-child")[0]; 
//or
//if you have the actual DOM element
var lastChild = $(element).select(":last-child")[0];

    Code in Jquery

    //if you only have the id of the parent
var lastChild = $("#parent :last-child")[0]; 
//or
//if you have the actual DOM element
var lastChild = $(":last-child", element)[0];

    Code in plain vanilla javascript

    var element = document.getElementById("parent");
var lastChild = element.childNodes[element.childNodes.length - 1];

    Also note that these can return null if the parent element has no child nodes.