# Yahoo! UI Library

### dom 3.0.0

Yahoo! UI Library > dom > selector-css3.js (source view)
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    /**
     * The selector css3 module provides support for css3 selectors.
     * @module dom
     * @submodule selector-css3
     * @for Selector
     */

    /*
        an+b = get every _a_th node starting at the _b_th
        0n+b = no repeat ("0" and "n" may both be omitted (together) , e.g. "0n+1" or "1", not "0+1"), return only the _b_th element
        1n+b =  get every element starting from b ("1" may may be omitted, e.g. "1n+0" or "n+0" or "n")
        an+0 = get every _a_th element, "0" may be omitted
    */

    Y.Selector._reNth = /^(?:([\-]?\d*)(n){1}|(odd|even)$)*([\-+]?\d*)$/;

    Y.Selector._getNth = function(node, expr, tag, reverse) {
        Y.Selector._reNth.test(expr);
        var a = parseInt(RegExp.$1, 10), // include every _a_ elements (zero means no repeat, just first _a_)
            n = RegExp.$2, // "n"
            oddeven = RegExp.$3, // "odd" or "even"
            b = parseInt(RegExp.$4, 10) || 0, // start scan from element _b_
            result = [],
            siblings = Y.Selector._children(node.parentNode, tag),
            op;

        if (oddeven) {
            a = 2; // always every other
            op = '+';
            n = 'n';
            b = (oddeven === 'odd') ? 1 : 0;
        } else if ( isNaN(a) ) {
            a = (n) ? 1 : 0; // start from the first or no repeat
        }

        if (a === 0) { // just the first
            if (reverse) {
                b = siblings.length - b + 1;
            }

            if (siblings[b - 1] === node) {
                return true;
            } else {
                return false;
            }

        } else if (a < 0) {
            reverse = !!reverse;
            a = Math.abs(a);
        }

        if (!reverse) {
            for (var i = b - 1, len = siblings.length; i < len; i += a) {
                if ( i >= 0 && siblings[i] === node ) {
                    return true;
                }
            }
        } else {
            for (var i = siblings.length - b, len = siblings.length; i >= 0; i -= a) {
                if ( i < len && siblings[i] === node ) {
                    return true;
                }
            }
        }
        return false;
    };

    Y.mix(Y.Selector.pseudos, {
        'root': function(node) {
            return node === node.ownerDocument.documentElement;
        },

        'nth-child': function(node, expr) {
            return Y.Selector._getNth(node, expr);
        },

        'nth-last-child': function(node, expr) {
            return Y.Selector._getNth(node, expr, null, true);
        },

        'nth-of-type': function(node, expr) {
            return Y.Selector._getNth(node, expr, node.tagName);
        },

        'nth-last-of-type': function(node, expr) {
            return Y.Selector._getNth(node, expr, node.tagName, true);
        },

        'last-child': function(node) {
            var children = Y.Selector._children(node.parentNode);
            return children[children.length - 1] === node;
        },

        'first-of-type': function(node) {
            return Y.Selector._children(node.parentNode, node.tagName)[0] === node;
        },

        'last-of-type': function(node) {
            var children = Y.Selector._children(node.parentNode, node.tagName);
            return children[children.length - 1] === node;
        },

        'only-child': function(node) {
            var children = Y.Selector._children(node.parentNode);
            return children.length === 1 && children[0] === node;
        },

        'only-of-type': function(node) {
            var children = Y.Selector._children(node.parentNode, node.tagName);
            return children.length === 1 && children[0] === node;
        },

        'empty': function(node) {
            return node.childNodes.length === 0;
        },

        'not': function(node, expr) {
            return !Y.Selector.test(node, expr);
        },

        'contains': function(node, expr) {
            var text = node.innerText || node.textContent || '';
            return text.indexOf(expr) > -1;
        },

        'checked': function(node) {
            return node.checked === true;
        }
    });

    Y.mix(Y.Selector.operators, {
        '^=': '^{val}', // Match starts with value
        '$=': '{val}$', // Match ends with value
        '*=': '{val}' // Match contains value as substring
    });

    Y.Selector.combinators['~'] = {
        axis: 'previousSibling'
    };

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