jquery_1.2.6版本中的nth函数

jquery1.2.6 版本的 nth函数

jQuery.each

next: function(elem){return jQuery.nth(elem,2,"nextSibling");},
prev: function(elem){return jQuery.nth(elem,2,"previousSibling");}

...省略部分代码
function(name, fn) {
jQuery.fn[ name ] = function( selector ) {
	var ret = jQuery.map( this, fn );

	if ( selector && typeof selector == "string" )
		ret = jQuery.multiFilter( selector, ret );

		return this.pushStack( jQuery.unique( ret ) );
	};
}

jquery对象函数next,prev中都用到了jQuery的静态函数nth：

nth: function(cur,result,dir,elem){
	result = result || 1;
	var num = 0;

	for ( ; cur; cur = cur[dir] )
		if ( cur.nodeType == 1 && ++num == result )
			break;

	return cur;
}

jQuery.map

再来看看1.2.6版本的map函数:

map: function( elems, callback ) {
	var ret = [];

	// Go through the array, translating each of the items to their
	// new value (or values).
	//调用callback函数返回新值
	for ( var i = 0, length = elems.length; i < length; i++ ) {
		var value = callback( elems[ i ], i );

		if ( value != null )
			ret[ ret.length ] = value;
	}

	return ret.concat.apply( [], ret );
}

jQuery.unique

unique: function( array ) {
	var ret = [], done = {};

	try {

		for ( var i = 0, length = array.length; i < length; i++ ) {
			var id = jQuery.data( array[ i ] );

			if ( !done[ id ] ) {
				done[ id ] = true;
				ret.push( array[ i ] );
			}
		}

	} catch( e ) {
		ret = array;
	}

	return ret;
}

jQuery.data

在each方法中用到了jQuery.data方法，我们来看看：

data: function( elem, name, data ) {
	elem = elem == window ?
		windowData :
		elem;

	var id = elem[ expando ];

	// Compute a unique ID for the element
	if ( !id )
		id = elem[ expando ] = ++uuid;

	// Only generate the data cache if we're
	// trying to access or manipulate it
	if ( name && !jQuery.cache[ id ] )
		jQuery.cache[ id ] = {};

	// Prevent overriding the named cache with undefined values
	if ( data !== undefined )
		jQuery.cache[ id ][ name ] = data;

	// Return the named cache data, or the ID for the element
	return name ?
		jQuery.cache[ id ][ name ] :
		id;
}

expando和uuid是这样定义的：

var expando = "jQuery" + now(), uuid = 0