jQuery.fn.find( selector )

if ( typeof selector !== "string" ) {
 self = this;
 return this.pushStack( jQuery( selector ).filter(function() {
  for ( i = 0; i < len; i++ ) {
   if ( jQuery.contains( self[ i ], this ) ) {
    return true;
   }
  }
 }) );
}

ret = [];
for ( i = 0; i < len; i++ ) {
 //第二個(gè)參數(shù)是表示context
 jQuery.find( selector, this[ i ], ret );
}
//$( selector, context )變成$( context ).find( selector )，需要去重和pushStack
ret = this.pushStack( len > 1 ? jQuery.unique( ret ) : ret );
ret.selector = ( this.selector ? this.selector + " " : "" ) + selector;
return ret;

jQuery.fn.closest( selectors, context )

pos = rneedsContext.test( selectors ) || typeof selectors !== "string" ?
jQuery( selectors, context || this.context ) :
0;

for ( ; i < l; i++ ) {
 cur = this[i];
 while ( cur && cur.ownerDocument && cur !== context && cur.nodeType !== 11 ) {
  if ( pos ? pos.index(cur) > -1 : jQuery.find.matchesSelector(cur, selectors) ) {
   ret.push( cur );
   break;
  }
  cur = cur.parentNode;
 }
}
return this.pushStack( ret.length > 1 ? jQuery.unique( ret ) : ret );

jQuery.each({
  parent: function( elem ) {…},
  parents: function( elem ) {…},
  parentsUntil: function( elem, i, until ) {…},
  next: function( elem ) {…},
  prev: function( elem ) {…},
  nextAll: function( elem ) {…},
  prevAll: function( elem ) {…},
  nextUntil: function( elem, i, until ) {…},
  prevUntil: function( elem, i, until ) {…},
  siblings: function( elem ) {…},
  children: function( elem ) {…},
  contents: function( elem ) {…}
 }, function( name, fn ) {
  jQuery.fn[ name ] = function( until, selector ) {
   var ret = jQuery.map( this, fn, until );
   //過濾
   ...
   return this.pushStack( ret );
  };
 });

if ( !runtil.test( name ) ) {
 selector = until;
}

if ( selector && typeof selector === "string" ) {
 ret = jQuery.filter( selector, ret );
}

ret = this.length > 1 && !guaranteedUnique[ name ] ? jQuery.unique( ret ) : ret;

if ( this.length > 1 && rparentsprev.test( name ) ) {
 ret = ret.reverse();
}

return this.pushStack( ret );　

dir: function( elem, dir, until ) {
 var matched = [],
 cur = elem[ dir ];
 while ( cur && cur.nodeType !== 9 && (until === undefined || cur.nodeType !== 1 || !jQuery( cur ).is( until )) ) {
  if ( cur.nodeType === 1 ) {
   matched.push( cur );
  }
  cur = cur[dir];
 }
 return matched;
},
//獲取節(jié)點(diǎn)n及其兄弟節(jié)點(diǎn)中非elem的節(jié)點(diǎn)集合r
sibling: function( n, elem ) {
 var r = [];
 for ( ; n; n = n.nextSibling ) {
  if ( n.nodeType === 1 && n !== elem ) {
   r.push( n );
  }
 }
 return r;
}
//找到當(dāng)前元素cur的下一個(gè)dir為止
function sibling( cur, dir ) {
  do {
   cur = cur[ dir ];
  } while ( cur && cur.nodeType !== 1 );
  return cur;
 }　

jQuery.fn.add( selector, context )和jQuery.fn. addBack( selector )

add: function( selector, context ) {
 var set = typeof selector === "string" ?
   jQuery( selector, context ) :
   jQuery.makeArray( selector && selector.nodeType ? [ selector ] : selector ),
  //把selector表達(dá)式獲取的結(jié)果集拼接到當(dāng)前對(duì)象上
  all = jQuery.merge( this.get(), set );
 //返回新的拼接結(jié)果
 return this.pushStack( jQuery.unique(all) );
}
　　jQuery.fn.add和jQuery.fn.not相對(duì)應(yīng)。jQuery.fn.not后面再說。
　　jQuery.fn.addBack將之前匹配的元素加入到當(dāng)前匹配的元素中，并以新的jQuery對(duì)象的形式返回。
addBack: function( selector ) {
 return this.add( selector == null ?
  this.prevObject : this.prevObject.filter(selector)
  );
}
jQuery.fn.andSelf = jQuery.fn.addBack;
　　
jQuery.fn.not( selector )和jQuery.fn.filter( selector )
not: function( selector ) {
 return this.pushStack( winnow(this, selector, false) );
}
filter: function( selector ) {
 return this.pushStack( winnow(this, selector, true) );
},

//執(zhí)行相同的過濾或者不過濾的功能
function winnow( elements, qualifier, keep ) {
 // Can't pass null or undefined to indexOf in Firefox 4
 // Set to 0 to skip string check
 qualifier = qualifier || 0;
 //如果過濾條件是函數(shù)，則通過過濾函數(shù)過濾
 if ( jQuery.isFunction( qualifier ) ) {
  return jQuery.grep(elements, function( elem, i ) {
   var retVal = !!qualifier.call( elem, i, elem );
   return retVal === keep;
  });
 //如果過濾條件是DOM相關(guān)類型，通過比較節(jié)點(diǎn)是否相同來過濾
 } else if ( qualifier.nodeType ) {
  return jQuery.grep(elements, function( elem ) {
   return ( elem === qualifier ) === keep;
  });
 //如果過濾條件是字符串
 } else if ( typeof qualifier === "string" ) {
  //過濾出elements中的節(jié)點(diǎn)元素
  var filtered = jQuery.grep(elements, function( elem ) {
   return elem.nodeType === 1;
  });
  // 其中isSimple = /^.[^:#\[\.,]*$/
  if ( isSimple.test( qualifier ) ) {
   return jQuery.filter(qualifier, filtered, !keep);
  } else {
   //查找filtered中滿足篩選條件qualifier的節(jié)點(diǎn)
   qualifier = jQuery.filter( qualifier, filtered );
  }
 }
 //過濾出elements中滿足過濾條件的元素
 return jQuery.grep(elements, function( elem ) {
  return ( jQuery.inArray( elem, qualifier ) >= 0 ) === keep;
 });
}

jQuery.filter: function( expr, elems, not ) {
 if ( not ) {
  expr = ":not(" + expr + ")";
 }
 //其中matchesSelector和matches是Sizzle中的函數(shù)。matchesSelector是判斷單個(gè)元素elem是否滿足表達(dá)式expr，matches是查找元素集合elems中滿足表達(dá)式expr的項(xiàng)
 return elems.length === 1 ?
  jQuery.find.matchesSelector(elems[0], expr) ? [ elems[0] ] : [] :
  jQuery.find.matches(expr, elems);
},

jQuery.fn.index( elem )

if ( !elem ) {
 return ( this[0] && this[0].parentNode ) ? this.first().prevAll().length : -1;
}

if ( typeof elem === "string" ) {
 //在數(shù)組jQuery( elem )中搜索指定的值，并返回其索引值
 return jQuery.inArray( this[0], jQuery( elem ) );
}

return jQuery.inArray(elem.jquery ? elem[0] : elem, this );