沒有完全看明白，看來得從Sizzle1.8看起。這是Sizzle又一個分水嶺，引入了編譯函數機制。
(function(window, undefined) {
var i,
cachedruns,
Expr,
getText,
isXML,
compile,
outermostContext,
recompare,
sortInput,
// Local document vars
setDocument,
document,
docElem,
documentIsHTML,
rbuggyQSA,
rbuggyMatches,
matches,
contains,
// Instance-specific data
expando = "sizzle" + -(new Date()),
preferredDoc = window.document,
support = {},
dirruns = 0,
done = 0,
classCache = createCache(),
tokenCache = createCache(),
compilerCache = createCache(),
hasDuplicate = false,
sortOrder = function() {
return 0;
},
// General-purpose constants
strundefined = typeof undefined,
MAX_NEGATIVE = 1 << 31,
// Array methods
arr = [],
pop = arr.pop,
push_native = arr.push,
push = arr.push,
slice = arr.slice,
//用於判定元素是否在此數組內
indexOf = arr.indexOf || function(elem) {
var i = 0,
len = this.length;
for (; i < len; i++) {
if (this[i] === elem) {
return i;
}
}
return -1;
},
// Regular expressions
// 空白的正則 http://www.w3.org/TR/css3-selectors/#whitespace
whitespace = "[\\x20\\t\\r\\n\\f]",
// 類選擇器與標簽選擇器的正則 http://www.w3.org/TR/css3-syntax/#characters
characterEncoding = "(?:\\\\.|[\\w-]|[^\\x00-\\xa0])+",
//ID選擇器與標簽選擇器的正則，HTML5將ID的規則放寬，允許ID可以是純數字
// An unquoted value should be a CSS identifier http://www.w3.org/TR/css3-selectors/#attribute-selectors
// Proper syntax: http://www.w3.org/TR/CSS21/syndata.html#value-def-identifier
identifier = characterEncoding.replace("w", "w#"),
// 屬性選擇器的操作符 http://www.w3.org/TR/selectors/#attribute-selectors
operators = "([*^$|!~]?=)",
//屬性選擇器的正則
attributes = "\\[" + whitespace + "*(" + characterEncoding + ")" + whitespace +
"*(?:" + operators + whitespace + "*(?:(['\"])((?:\\\\.|[^\\\\])*?)\\3|(" + identifier + ")|)|)" + whitespace + "*\\]",
// 偽類的正則
pseudos = ":(" + characterEncoding + ")(?:\\(((['\"])((?:\\\\.|[^\\\\])*?)\\3|((?:\\\\.|[^\\\\()[\\]]|" + attributes.replace(3, 8) + ")*)|.*)\\)|)",
// 去掉兩端空白正則
rtrim = new RegExp("^" + whitespace + "+|((?:^|[^\\\\])(?:\\\\.)*)" + whitespace + "+$", "g"),
//並聯選擇器的正則
rcomma = new RegExp("^" + whitespace + "*," + whitespace + "*"),
//關系選擇器的正則
rcombinators = new RegExp("^" + whitespace + "*([\\x20\\t\\r\\n\\f>+~])" + whitespace + "*"),
rpseudo = new RegExp(pseudos),
ridentifier = new RegExp("^" + identifier + "$"),
matchExpr = {
"ID": new RegExp("^#(" + characterEncoding + ")"),
"CLASS": new RegExp("^\\.(" + characterEncoding + ")"),
"NAME": new RegExp("^\\[name=['\"]?(" + characterEncoding + ")['\"]?\\]"),
"TAG": new RegExp("^(" + characterEncoding.replace("w", "w*") + ")"),
"ATTR": new RegExp("^" + attributes),
"PSEUDO": new RegExp("^" + pseudos),
//子元素過濾偽類
"CHILD": new RegExp("^:(only|first|last|nth|nth-last)-(child|of-type)(?:\\(" + whitespace +
"*(even|odd|(([+-]|)(\\d*)n|)" + whitespace + "*(?:([+-]|)" + whitespace +
"*(\\d+)|))" + whitespace + "*\\)|)", "i"),
// 位置偽類
"needsContext": new RegExp("^" + whitespace + "*[>+~]|:(even|odd|eq|gt|lt|nth|first|last)(?:\\(" + whitespace + "*((?:-\\d)?\\d*)" + whitespace + "*\\)|)(?=[^-]|$)", "i")
},
rsibling = /[\x20\t\r\n\f]*[+~]/,
//取函數的toString判定是否原生API，比如一些庫偽造了getElementsByClassName
rnative = /^[^{]+\{\s*\[native code/,
//判定選擇符是否為單個ID選擇器，或標簽選擇器或類選擇器
rquickExpr = /^(?:#([\w-]+)|(\w+)|\.([\w-]+))$/,
//jQuery自定義的input偽類
rinputs = /^(?:input|select|textarea|button)$/i,
//jQuery自定義的header偽類
rheader = /^h\d$/i,
rescape = /'|\\/g,
//用於匹配不帶引號的屬性值,用於matchesSelector
rattributeQuotes = /\=[\x20\t\r\n\f]*([^'"\]]*)[\x20\t\r\n\f]*\]/g,
// CSS 字符轉義 http://www.w3.org/TR/CSS21/syndata.html#escaped-characters
runescape = /\\([\da-fA-F]{1,6}[\x20\t\r\n\f]?|.)/g,
funescape = function(_, escaped) {
var high = "0x" + escaped - 0x10000;
// NaN means non-codepoint
return high !== high ? escaped :
// BMP codepoint
high < 0 ? String.fromCharCode(high + 0x10000) :
// Supplemental Plane codepoint (surrogate pair)
String.fromCharCode(high >> 10 | 0xD800, high & 0x3FF | 0xDC00);
};
// 將一個NodeList轉換為一個純數組
try {
push.apply(
(arr = slice.call(preferredDoc.childNodes)),
preferredDoc.childNodes);
// Support: Android<4.0
// Detect silently failing push.apply
arr[preferredDoc.childNodes.length].nodeType;
} catch (e) {
push = {
apply: arr.length ?
// Leverage slice if possible
function(target, els) {
push_native.apply(target, slice.call(els));
} :
// IE6-8只能逐個遍歷加入
function(target, els) {
var j = target.length,
i = 0;
// Can't trust NodeList.length
while ((target[j++] = els[i++])) {}
target.length = j - 1;
}
};
}
function isNative(fn) {
return rnative.test(fn + "");
}
//創建一個緩存函數,它以自己為儲存倉庫,鍵名放到閉包內的一個數組內,當數組的個數超過
//Expr.cacheLength時,則去掉最前面的鍵值
function createCache() {
var cache,
keys = [];
return (cache = function(key, value) {
//對鍵名進行改造,防止與Object.prototype的原生方法重名,比如toString, valueOf th native prototype properties (see Issue #157)
if (keys.push(key += " ") > Expr.cacheLength) {
// Only keep the most recent entries
delete cache[keys.shift()];
}
return (cache[key] = value);
});
}
/**
* Mark a function for special use by Sizzle
* @param {Function} fn The function to mark
*/
function markFunction(fn) {
fn[expando] = true;
return fn;
}
//用於做各種特征檢測，比如是否支持某個API，API支持是否完美
function assert(fn) {
var div = document.createElement("div");
try {
return !!fn(div);
} catch (e) {
return false;
} finally {
// release memory in IE
div = null;
}
}
//Sizzle主函數被設計得能遞歸自身，參數依次是選擇符，上下文對象，結果集，種子集
//除了第一個參數，其他都是可選，上下文對象默認是當前文檔對象
function Sizzle(selector, context, results, seed) {
var match, elem, m, nodeType,
// QSA vars
i, groups, old, nid, newContext, newSelector;
//如果指定了上下文對象的ownerDocument不等於當前文檔對象，覆寫所有涉及到document的內部方法
if ((context ? context.ownerDocument || context : preferredDoc) !== document) {
setDocument(context);
}
context = context || document;
results = results || [];
if (!selector || typeof selector !== "string") {
return results;
}
if ((nodeType = context.nodeType) !== 1 && nodeType !== 9) {
return [];
}
if (documentIsHTML && !seed) {
// Shortcuts
if ((match = rquickExpr.exec(selector))) {
// Speed-up: Sizzle("#ID")
//如果只有一個ID，那么直接getElementById，然后判定其是否在DOM樹，
//元素的ID確實為目標值就將它合並到結果集中
if ((m = match[1])) {
if (nodeType === 9) {
elem = context.getElementById(m);
// Check parentNode to catch when Blackberry 4.6 returns
// nodes that are no longer in the document #6963
if (elem && elem.parentNode) {
// Handle the case where IE, Opera, and Webkit return items
// by name instead of ID
if (elem.id === m) {
results.push(elem);
return results;
}
} else {
return results;
}
} else {
//如果上下文非文檔對象，需要用contains函數進行驗證
if (context.ownerDocument && (elem = context.ownerDocument.getElementById(m)) && contains(context, elem) && elem.id === m) {
results.push(elem);
return results;
}
}
//如果選擇符為一個標簽選擇器
} else if (match[2]) {
push.apply(results, context.getElementsByTagName(selector));
return results;
//如果選擇符為一個類選擇器，瀏覽器又支持getElementsByClassName
} else if ((m = match[3]) && support.getElementsByClassName && context.getElementsByClassName) {
push.apply(results, context.getElementsByClassName(m));
return results;
}
}
// 嘗試使用querySelectorAll，並且選擇符不存在那些有問題的選擇器
if (!support.qsa && !rbuggyQSA.test(selector)) {
old = true;
nid = expando;
newContext = context;
newSelector = nodeType === 9 && selector;
//IE8的querySelectorAll實現存在BUG，它會在包含自己的集合內查找符合自己的元素節點
//根據規范，應該是當前上下文的所有子孫下找
//IE8下如果元素節點為Object，無法找到元素
if (nodeType === 1 && context.nodeName.toLowerCase() !== "object") {
groups = tokenize(selector); //將選擇符細分N個分組
//如果存在ID，則將ID取得出來放到這個分組的最前面，比如div b --> [id=xxx] div b
//不存在ID，就創建一個ID，重復上面的操作，但最后會刪掉此ID
if ((old = context.getAttribute("id"))) {
nid = old.replace(rescape, "\\$&");
} else {
context.setAttribute("id", nid);
}
nid = "[id='" + nid + "'] ";
i = groups.length;
while (i--) {
groups[i] = nid + toSelector(groups[i]);
}
newContext = rsibling.test(selector) && context.parentNode || context;
newSelector = groups.join(",");
}
if (newSelector) {
try {
push.apply(results,
newContext.querySelectorAll(newSelector));
return results;
} catch (qsaError) {} finally {
if (!old) {
context.removeAttribute("id");
}
}
}
}
}
// 否則去掉兩邊的空白開始查找
return select(selector.replace(rtrim, "$1"), context, results, seed);
}
/**
* Detect xml
* @param {Element|Object} elem An element or a document
*/
isXML = Sizzle.isXML = function(elem) {
// documentElement is verified for cases where it doesn't yet exist
// (such as loading iframes in IE - #4833)
var documentElement = elem && (elem.ownerDocument || elem).documentElement;
return documentElement ? documentElement.nodeName !== "HTML" : false;
};
/**
* Sets document-related variables once based on the current document
* @param {Element|Object} [doc] An element or document object to use to set the document
* @returns {Object} Returns the current document
*/
setDocument = Sizzle.setDocument = function(node) {
var doc = node ? node.ownerDocument || node : preferredDoc;
//如果文檔對象等於當前文檔對象，無法確認其文檔對象，或沒有HTML，直接返回
//此情況出現機率接近零
if (doc === document || doc.nodeType !== 9 || !doc.documentElement) {
return document;
}
// Set our document
document = doc;
docElem = doc.documentElement;
// 是否為HTML文檔
documentIsHTML = !isXML(doc);
//判定getElementsByTagName("*")是否只返回元素節點，IE6-8會混雜注釋節點
support.getElementsByTagName = assert(function(div) {
div.appendChild(doc.createComment(""));
return !div.getElementsByTagName("*").length;
});
//判定瀏覽器是否區分property與attribute，比如下面測試，multiple為select的一個property
//只能通過el.xxx這樣的方法去取值，若使用getAttribute去取會返回null
support.attributes = assert(function(div) {
div.innerHTML = "<select></select>";
var type = typeof div.lastChild.getAttribute("multiple");
// IE8 returns a string for some attributes even when not present
return type !== "boolean" && type !== "string";
});
//判定getElementsByClassName值得信任，比如下面測試發現opera9.6不支持第二個類名，
//safari3.2緩存過度，忘了更新自身
support.getElementsByClassName = assert(function(div) {
div.innerHTML = "<div class='hidden e'></div><div class='hidden'></div>";
if (!div.getElementsByClassName || !div.getElementsByClassName("e").length) {
return false; //opera9.6
}
// Safari 3.2
div.lastChild.className = "e";
return div.getElementsByClassName("e").length === 2;
});
// 判定getElementsByName是否可用Check if getElementsByName privileges form controls or returns elements by ID
// If so, assume (for broader support) that getElementById returns elements by name
support.getByName = assert(function(div) {
div.id = expando + 0; //用於檢測是否區分name與ID
// getElementsByName是一個問題多的API，Sizzle原來的注釋透露多少東西，
//因此我在這里補上
//1 IE6-7下getElementsByName與getElementById都不區分元素的name與ID
//2 IE的getElementsByName只對表單元素有效，無視擁有相同name值的span div元素
//3 IE6-7下即使通過document.createElement創建一個表單元素，動態設置name與插入
// DOM樹，getElementsByName無法找到此元素，innerHTML也不行。一定需要以
// document.createElement("<input name="aaa"/>")方式生成元素才行。
// 同樣的情況也發生在iframe上，IE6-7的iframe的name也需要這樣同時生成。
//4 name本來是一個property，但標准瀏覽器好像已經默認setAttribute("name","xxx")
// 也能被getElementsByName獲取到。
//5 IE6-8通過innerHTML生成包含name屬性的元素時,可能發生無法捕獲的錯誤
div.appendChild(document.createElement("a")).setAttribute("name", expando);
div.appendChild(document.createElement("i")).setAttribute("name", expando);
docElem.appendChild(div);
// Test
var pass = doc.getElementsByName &&
// buggy browsers will return fewer than the correct 2
doc.getElementsByName(expando).length === 2 +
// buggy browsers will return more than the correct 0
doc.getElementsByName(expando + 0).length;
// Cleanup
docElem.removeChild(div);
return pass;
});
// Support: Webkit<537.32
// 判定compareDocumentPosition是否可靠
support.sortDetached = assert(function(div1) {
return div1.compareDocumentPosition &&
// Should return 1, but Webkit returns 4 (following)
(div1.compareDocumentPosition(document.createElement("div")) & 1);
});
// 調整IE6-7下獲取某些屬性的方式，這里只對href, type進行處理
//實際上，在jQuery里它會被jQuery.attr覆蓋
Expr.attrHandle = assert(function(div) {
div.innerHTML = "<a href='#'></a>";
//IE取href, action, src時不會原型返回，會返回其絕對路徑
return div.firstChild && typeof div.firstChild.getAttribute !== strundefined && div.firstChild.getAttribute("href") === "#";
}) ? {} : {
"href": function(elem) {
return elem.getAttribute("href", 2);
},
"type": function(elem) {
return elem.getAttribute("type");
}
};
// ID find and filter
if (support.getByName) {
Expr.find["ID"] = function(id, context) {
//Blackberry 4.6 緩存過度，即便這元素被移出DOM樹也能找到
if (typeof context.getElementById !== strundefined && documentIsHTML) {
var m = context.getElementById(id);
return m && m.parentNode ? [m] : [];
}
};
Expr.filter["ID"] = function(id) { //過濾器
var attrId = id.replace(runescape, funescape);
return function(elem) {
return elem.getAttribute("id") === attrId;
};
};
} else {
Expr.find["ID"] = function(id, context) {
if (typeof context.getElementById !== strundefined && documentIsHTML) {
var m = context.getElementById(id);
//1 IE6-7無法區分name與ID，
//2 如果form元素的ID為aaa，它下面也有一個name為aaa的INPUT元素，會錯誤返回INPUT
return m ? m.id === id || typeof m.getAttributeNode !== strundefined && m.getAttributeNode("id").value === id ? [m] : undefined : [];
}
};
Expr.filter["ID"] = function(id) {
var attrId = id.replace(runescape, funescape);
return function(elem) {
var node = typeof elem.getAttributeNode !== strundefined && elem.getAttributeNode("id");
return node && node.value === attrId;
};
};
}
// Tag
Expr.find["TAG"] = support.getElementsByTagName ? function(tag, context) {
if (typeof context.getElementsByTagName !== strundefined) {
return context.getElementsByTagName(tag);
}
} : function(tag, context) {
var elem,
tmp = [],
i = 0,
results = context.getElementsByTagName(tag);
// 過濾注釋節點
if (tag === "*") {
while ((elem = results[i++])) {
if (elem.nodeType === 1) {
tmp.push(elem);
}
}
return tmp;
}
return results;
};
// Name
Expr.find["NAME"] = support.getByName && function(tag, context) {
if (typeof context.getElementsByName !== strundefined) {
return context.getElementsByName(name);
}
};
// Class
Expr.find["CLASS"] = support.getElementsByClassName && function(className, context) {
if (typeof context.getElementsByClassName !== strundefined && documentIsHTML) {
return context.getElementsByClassName(className);
}
};
rbuggyMatches = [];
rbuggyQSA = [":focus"];
//querySelectorAll可以說得上兼容性最差的API，每個瀏覽器每個版本可能都有差異
//IE8只支持到CSS2，
//對於focus偽類,其實現在除opera，safari外，其他瀏覽器取:focus都正常,
//但這個東西實在很難在程序來偵測，jQuery選擇了一刀切
if ((support.qsa = isNative(doc.querySelectorAll))) {
assert(function(div) {
//對於布爾屬性，只要是顯式設置了無論值是什么，selected都為false，且通過屬性選擇器都能選取到
//這個在IE下有BUG
div.innerHTML = "<select><option selected=''></option></select>";
//如果為零，則把常見的布爾屬性都放到buggy列表中
// IE8 - Some boolean attributes are not treated correctly
if (!div.querySelectorAll("[selected]").length) {
rbuggyQSA.push("\\[" + whitespace + "*(?:checked|disabled|ismap|multiple|readonly|selected|value)");
}
//根據W3C標准,：checked應該包含被選中的option元素，IE8失敗
// Webkit/Opera - :checked should return selected option elements
// http://www.w3.org/TR/2011/REC-css3-selectors-20110929/#checked
if (!div.querySelectorAll(":checked").length) {
rbuggyQSA.push(":checked");
}
});
assert(function(div) {
//如果屬性值為空字符串，那么對於^= $= *=等操作符直接返回false，不會被匹配，opera10-12/IE8都不正確
div.innerHTML = "<input type='hidden' i=''/>";
if (div.querySelectorAll("[i^='']").length) {
rbuggyQSA.push("[*^$]=" + whitespace + "*(?:\"\"|'')");
}
//firefox3.5無法對隱藏元素取:enabled/:disabled偽類，而IE8則直接拋錯
if (!div.querySelectorAll(":enabled").length) {
rbuggyQSA.push(":enabled", ":disabled");
}
// Opera 10-11對於非法偽類不會拋錯
div.querySelectorAll("*,:x");
rbuggyQSA.push(",.*:");
});
}
//判定是否支持matchesSelector，如果不支持，看它是否存在帶私有前綴的近親
if ((support.matchesSelector = isNative((matches = docElem.matchesSelector || docElem.mozMatchesSelector || docElem.webkitMatchesSelector || docElem.oMatchesSelector || docElem.msMatchesSelector)))) {
assert(function(div) {
//IE9緩存過度，能匹配移出DOM樹的節點
support.disconnectedMatch = matches.call(div, "div");
//Gecko對於非法選擇符不會拋錯，而是返回false
matches.call(div, "[s!='']:x");
rbuggyMatches.push("!=", pseudos);
});
}
rbuggyQSA = new RegExp(rbuggyQSA.join("|"));
rbuggyMatches = rbuggyMatches.length && new RegExp(rbuggyMatches.join("|"));
//重寫contains，有原生API就用原生API，否則就遍歷DOM樹
contains = isNative(docElem.contains) || docElem.compareDocumentPosition ? function(a, b) {
var adown = a.nodeType === 9 ? a.documentElement : a,
bup = b && b.parentNode;
return a === bup || !! (bup && bup.nodeType === 1 && (
adown.contains ? adown.contains(bup) : a.compareDocumentPosition && a.compareDocumentPosition(bup) & 16));
} : function(a, b) {
if (b) {
while ((b = b.parentNode)) {
if (b === a) {
return true;
}
}
}
return false;
};
// 重寫比較函數
sortOrder = function(a, b) {
//略
}
};
//判定這些元素是否匹配expr
Sizzle.matches = function(expr, elements) {
return Sizzle(expr, null, null, elements);
};
Sizzle.matchesSelector = function(elem, expr) {
// Set document vars if needed
if ((elem.ownerDocument || elem) !== document) {
setDocument(elem);
}
//IE9的querySelectorAll要求屬性選擇器的值必須被引起來
expr = expr.replace(rattributeQuotes, "='$1']");
//優化使用原生API
if (support.matchesSelector && documentIsHTML && (!rbuggyMatches || !rbuggyMatches.test(expr)) && !rbuggyQSA.test(expr)) {
try {
var ret = matches.call(elem, expr);
if (ret || support.disconnectedMatch || elem.document && elem.document.nodeType !== 11) {
return ret;
}
} catch (e) {}
}
return Sizzle(expr, document, null, [elem]).length > 0;
};
Sizzle.contains = function(context, elem) {
// Set document vars if needed
if ((context.ownerDocument || context) !== document) {
setDocument(context);
}
return contains(context, elem);
};
Sizzle.attr = function(elem, name) {
var val;
// Set document vars if needed
if ((elem.ownerDocument || elem) !== document) {
setDocument(elem);
}
//HTML統一對屬性名小寫化
if (documentIsHTML) {
name = name.toLowerCase();
}
if ((val = Expr.attrHandle[name])) {
return val(elem);
}
if (!documentIsHTML || support.attributes) {
return elem.getAttribute(name);
}
return ((val = elem.getAttributeNode(name)) || elem.getAttribute(name)) && elem[name] === true ? name : val && val.specified ? val.value : null;
};
Sizzle.error = function(msg) {
throw new Error("Syntax error, unrecognized expression: " + msg);
};
Sizzle.uniqueSort = function(results) {
//去重排序
var elem,
duplicates = [],
j = 0,
i = 0;
// Unless we *know* we can detect duplicates, assume their presence
hasDuplicate = !support.detectDuplicates;
// Compensate for sort limitations
recompare = !support.sortDetached;
sortInput = !support.sortStable && results.slice(0);
results.sort(sortOrder);
if (hasDuplicate) {
while ((elem = results[i++])) {
if (elem === results[i]) {
j = duplicates.push(i);
}
}
while (j--) {
results.splice(duplicates[j], 1);
}
}
return results;
};
function siblingCheck(a, b) {
//比較同一個父親下,兩個元素節點的先后順序
var cur = b && a,
diff = cur && (~b.sourceIndex || MAX_NEGATIVE) - (~a.sourceIndex || MAX_NEGATIVE);
// Use IE sourceIndex if available on both nodes
if (diff) {
return diff;
}
// Check if b follows a
if (cur) {
while ((cur = cur.nextSibling)) {
if (cur === b) {
return -1;
}
}
}
return a ? 1 : -1;
}
//創建一個偽類的過濾函數,此方法是根據表單元素的type值生成
//比如:radio, :text, :checkbox, :file, :image等自定義偽類
function createInputPseudo(type) {
return function(elem) {
var name = elem.nodeName.toLowerCase();
return name === "input" && elem.type === type;
};
}
//創建一個偽類的過濾函數,此方法是根據表單元素的type值或標簽類型生成
//如果:button, :submit自定義偽類
function createButtonPseudo(type) {
return function(elem) {
var name = elem.nodeName.toLowerCase();
return (name === "input" || name === "button") && elem.type === type;
};
}
//用於創建位置偽類的過濾函數，它們是模擬從左向右的順序進行選擇，
//匹配到它時的結果集的位置來挑選元素的
//比如:odd,:even, :eq, :gt, :lt, :first, :last
function createPositionalPseudo(fn) {
return markFunction(function(argument) {
argument = +argument;
return markFunction(function(seed, matches) {
var j,
matchIndexes = fn([], seed.length, argument),
i = matchIndexes.length;
while (i--) {
if (seed[(j = matchIndexes[i])]) {
seed[j] = !(matches[j] = seed[j]);
}
}
});
});
}
/**
* Utility function for retrieving the text value of an array of DOM nodes
* @param {Array|Element} elem
*/
//用於:contains偽類，用於匹配當前元素的textConten是否包含目標字符串
//但對於XML，則需要逐個取得它里面的文本節點，CDATA節點的nodeValue進行拼接了
getText = Sizzle.getText = function(elem) {
var node,
ret = "",
i = 0,
nodeType = elem.nodeType;
if (!nodeType) {
// If no nodeType, this is expected to be an array
for (;
(node = elem[i]); i++) {
// Do not traverse comment nodes
ret += getText(node);
}
} else if (nodeType === 1 || nodeType === 9 || nodeType === 11) {
if (typeof elem.textContent === "string") {
return elem.textContent;
} else {
// Traverse its children
for (elem = elem.firstChild; elem; elem = elem.nextSibling) {
ret += getText(elem);
}
}
} else if (nodeType === 3 || nodeType === 4) {
return elem.nodeValue;
}
// Do not include comment or processing instruction nodes
return ret;
};
Expr = Sizzle.selectors = {
// Can be adjusted by the user
cacheLength: 50,
createPseudo: markFunction,
match: matchExpr,
find: {},
relative: {
">": {
dir: "parentNode",
first: true
},
" ": {
dir: "parentNode"
},
"+": {
dir: "previousSibling",
first: true
},
"~": {
dir: "previousSibling"
}
},
preFilter: {
//預處理，有的選擇器，比如屬性選擇器與偽類從選擇器組分割出來，還要再細分
//屬性選擇器要切成屬性名，屬性值，操作符；偽類要切為類型與傳參；
//子元素過濾偽類還要根據an+b的形式再划分
"ATTR": function(match) {
match[1] = match[1].replace(runescape, funescape);
// Move the given value to match[3] whether quoted or unquoted
match[3] = (match[4] || match[5] || "").replace(runescape, funescape);
if (match[2] === "~=") {
match[3] = " " + match[3] + " ";
}
return match.slice(0, 4);
},
"CHILD": function(match) {
//將它的偽類名稱與傳參拆分為更細的單元,以數組形式返回
//比如 ":nth-child(even)"變為
//["nth","child","even", 2, 0, undefined, undefined, undefined]
},
"PSEUDO": function(match) {
//將它的偽類名稱與傳參進行再處理
//比如:contains偽類會去掉兩邊的引號,反義偽類括號部分會再次提取
}
},
filter: {
//過濾函數（它們基本上都是curry）
"TAG": function(nodeName) { //標簽選擇器
if (nodeName === "*") {
return function() {
return true;
};
}
nodeName = nodeName.replace(runescape, funescape).toLowerCase();
return function(elem) {
return elem.nodeName && elem.nodeName.toLowerCase() === nodeName;
};
},
"CLASS": function(className) { //類選擇器，創建一個正則進行匹配
var pattern = classCache[className + " "];
return pattern || (pattern = new RegExp("(^|" + whitespace + ")" + className + "(" + whitespace + "|$)")) && classCache(className, function(elem) {
return pattern.test(elem.className || (typeof elem.getAttribute !== strundefined && elem.getAttribute("class")) || "");
});
},
"ATTR": function(name, operator, check) {
return function(elem) { //屬性選擇器
var result = Sizzle.attr(elem, name);
if (result == null) {
return operator === "!=";
}
if (!operator) {
return true;
}
result += "";
//這里的三目運算符套嵌得非常復雜，可以參看一下EXT的DOMQuery或mass的Icarus的實現
return operator === "=" ? result === check : operator === "!=" ? result !== check : operator === "^=" ? check && result.indexOf(check) === 0 : operator === "*=" ? check && result.indexOf(check) > -1 : operator === "$=" ? check && result.slice(-check.length) === check : operator === "~=" ? (" " + result + " ").indexOf(check) > -1 : operator === "|=" ? result === check || result.slice(0, check.length + 1) === check + "-" : false;
};
},
"CHILD": function(type, what, argument, first, last) {
//這里處理子元素過濾偽類,如:nth-child, :first-child, :only-child
},
"PSEUDO": function(pseudo, argument) {
//這里各種偽類,分派給上方的"CHILD"與下方的"pseudos"去處理
}
},
pseudos: {
//這里包含各種偽類的過濾函數
//如:not,:lang,:target,:root,:enabled,:disabled,:checked, :empty(原生偽類)
//parent, :has,:contains(源自xpath的自定義偽類)
// :header,:input,:text,:radio,:checkbox,:submit,:reset,
// :file,:password,:image(自定義標簽偽類)
// :last,:first,:last, :eq, :even, :odd, :lt,:gt(自定義位置偽類)
}
};
function tokenize(selector, parseOnly) {
var matched, match, tokens, type,
soFar, groups, preFilters,
cached = tokenCache[selector + " "];
//先查看緩存了沒有
if (cached) {
return parseOnly ? 0 : cached.slice(0);
}
soFar = selector;
groups = [];//這是最后要返回的結果，一個二維數組
//比如"title,div > :nth-child(even)"解析下面的符號流
// [ [{value:"title",type:"TAG",matches:["title"]}],
// [{value:"div",type:["TAG",matches:["div"]},
// {value:">", type: ">"},
// {value:":nth-child(even)",type:"CHILD",matches:["nth",
// "child","even",2,0,undefined,undefined,undefined]}
// ]
// ]
//有多少個並聯選擇器，里面就有多少個數組，數組里面是擁有value與type的對象
preFilters = Expr.preFilter;
while (soFar) {
// 以第一個逗號切割選擇符,然后去掉前面的部分
if (!matched || (match = rcomma.exec(soFar))) {
if (match) {
// Don't consume trailing commas as valid
soFar = soFar.slice(match[0].length) || soFar;
}
groups.push(tokens = []);
}
matched = false;
//將剛才前面的部分以關系選擇器再進行划分
if ((match = rcombinators.exec(soFar))) {
matched = match.shift();
tokens.push({
value: matched,
// Cast descendant combinators to space
type: match[0].replace(rtrim, " ")
});
soFar = soFar.slice(matched.length);
}
//將每個選擇器組依次用ID,TAG,CLASS,ATTR,CHILD,PSEUDO這些正則進行匹配
for (type in Expr.filter) {//preFilters是用於分析選擇器的名字與參數
if ((match = matchExpr[type].exec(soFar)) && (!preFilters[type] || (match = preFilters[type](match)))) {
matched = match.shift();
tokens.push({
value: matched,
type: type,
matches: match
});
soFar = soFar.slice(matched.length);
}
}
if (!matched) {
break;
}
}
return parseOnly ? soFar.length : soFar ? Sizzle.error(selector) :
// 放到tokenCache函數里進行緩存
tokenCache(selector, groups).slice(0);
}
function toSelector(tokens) {
var i = 0,//將符合流重新組合成選擇符，這時能把多余的空白去掉
len = tokens.length,
selector = "";
for (; i < len; i++) {
selector += tokens[i].value;
}
return selector;
}
function addCombinator(matcher, combinator, base) {
var dir = combinator.dir,
checkNonElements = base && dir === "parentNode",
doneName = done++;
return combinator.first ?
// Check against closest ancestor/preceding element
function(elem, context, xml) {
while ((elem = elem[dir])) {
if (elem.nodeType === 1 || checkNonElements) {
return matcher(elem, context, xml);
}
}
} :
// Check against all ancestor/preceding elements
function(elem, context, xml) {
var data, cache, outerCache,
dirkey = dirruns + " " + doneName;
// We can't set arbitrary data on XML nodes, so they don't benefit from dir caching
if (xml) {
while ((elem = elem[dir])) {
if (elem.nodeType === 1 || checkNonElements) {
if (matcher(elem, context, xml)) {
return true;
}
}
}
} else {
while ((elem = elem[dir])) {
if (elem.nodeType === 1 || checkNonElements) {
outerCache = elem[expando] || (elem[expando] = {});
if ((cache = outerCache[dir]) && cache[0] === dirkey) {
if ((data = cache[1]) === true || data === cachedruns) {
return data === true;
}
} else {
cache = outerCache[dir] = [dirkey];
cache[1] = matcher(elem, context, xml) || cachedruns;
if (cache[1] === true) {
return true;
}
}
}
}
}
};
}
function elementMatcher(matchers) {
return matchers.length > 1 ? function(elem, context, xml) {
var i = matchers.length;
while (i--) {
if (!matchers[i](elem, context, xml)) {
return false;
}
}
return true;
} : matchers[0];
}
function condense(unmatched, map, filter, context, xml) {
var elem,
newUnmatched = [],
i = 0,
len = unmatched.length,
mapped = map != null;
for (; i < len; i++) {
if ((elem = unmatched[i])) {
if (!filter || filter(elem, context, xml)) {
newUnmatched.push(elem);
if (mapped) {
map.push(i);
}
}
}
}
return newUnmatched;
}
function setMatcher(preFilter, selector, matcher, postFilter, postFinder, postSelector) {
if (postFilter && !postFilter[expando]) {
postFilter = setMatcher(postFilter);
}
if (postFinder && !postFinder[expando]) {
postFinder = setMatcher(postFinder, postSelector);
}
return markFunction(function(seed, results, context, xml) {
var temp, i, elem,
preMap = [],
postMap = [],
preexisting = results.length,
// Get initial elements from seed or context
elems = seed || multipleContexts(selector || "*", context.nodeType ? [context] : context, []),
// Prefilter to get matcher input, preserving a map for seed-results synchronization
matcherIn = preFilter && (seed || !selector) ? condense(elems, preMap, preFilter, context, xml) : elems,
matcherOut = matcher ?
// If we have a postFinder, or filtered seed, or non-seed postFilter or preexisting results,
postFinder || (seed ? preFilter : preexisting || postFilter) ?
// ...intermediate processing is necessary
[] :
// ...otherwise use results directly
results : matcherIn;
// Find primary matches
if (matcher) {
matcher(matcherIn, matcherOut, context, xml);
}
// Apply postFilter
if (postFilter) {
temp = condense(matcherOut, postMap);
postFilter(temp, [], context, xml);
// Un-match failing elements by moving them back to matcherIn
i = temp.length;
while (i--) {
if ((elem = temp[i])) {
matcherOut[postMap[i]] = !(matcherIn[postMap[i]] = elem);
}
}
}
if (seed) {
if (postFinder || preFilter) {
if (postFinder) {
// Get the final matcherOut by condensing this intermediate into postFinder contexts
temp = [];
i = matcherOut.length;
while (i--) {
if ((elem = matcherOut[i])) {
// Restore matcherIn since elem is not yet a final match
temp.push((matcherIn[i] = elem));
}
}
postFinder(null, (matcherOut = []), temp, xml);
}
// Move matched elements from seed to results to keep them synchronized
i = matcherOut.length;
while (i--) {
if ((elem = matcherOut[i]) && (temp = postFinder ? indexOf.call(seed, elem) : preMap[i]) > -1) {
seed[temp] = !(results[temp] = elem);
}
}
}
// Add elements to results, through postFinder if defined
} else {
matcherOut = condense(
matcherOut === results ? matcherOut.splice(preexisting, matcherOut.length) : matcherOut);
if (postFinder) {
postFinder(null, results, matcherOut, xml);
} else {
push.apply(results, matcherOut);
}
}
});
}
function matcherFromTokens(tokens) {
//生成用於匹配單個選擇器組的函數
}
function matcherFromGroupMatchers(elementMatchers, setMatchers) {
//生成用於匹配單個選擇器群組的函數
}
compile = Sizzle.compile = function(selector, group /* Internal Use Only */ ) {
var i,
setMatchers = [],
elementMatchers = [],
cached = compilerCache[selector + " "];
if (!cached) {
// Generate a function of recursive functions that can be used to check each element
if (!group) {
group = tokenize(selector);
}
i = group.length;
while (i--) {
//比如div:not(.aaa)跑到這里,group只剩下
//[[{value:":not(.aaa)",type:"PSEUDO",matches:["not","aaa"]}]
cached = matcherFromTokens(group[i]);
if (cached[expando]) {
setMatchers.push(cached);
} else {
elementMatchers.push(cached);
}
}
// Cache the compiled function
cached = compilerCache(selector, matcherFromGroupMatchers(elementMatchers, setMatchers));
}
return cached;
};
function multipleContexts(selector, contexts, results) {
var i = 0,
len = contexts.length;
for (; i < len; i++) {
Sizzle(selector, contexts[i], results);
}
return results;
}
function select(selector, context, results, seed) {
var i, tokens, token, type, find,
match = tokenize(selector);
if (!seed) {
// Try to minimize operations if there is only one group
if (match.length === 1) {//如果只有一個選擇器群組
tokens = match[0] = match[0].slice(0);
//如果里面包含ID選擇器， 比如#aaa > div
if (tokens.length > 2 && (token = tokens[0]).type === "ID" && context.nodeType === 9 && documentIsHTML && Expr.relative[tokens[1].type]) {
context = (Expr.find["ID"](token.matches[0].replace(runescape, funescape), context) || [])[0];
if (!context) {//如果最左邊的那個祖先都不存在，那么就不用找下去了
return results;
}
//將最初的選擇符去掉ID選擇器 ---> " > div"
selector = selector.slice(tokens.shift().value.length);
}
// Fetch a seed set for right-to-left matching
i = matchExpr["needsContext"].test(selector) ? 0 : tokens.length;
while (i--) {
token = tokens[i];
// Abort if we hit a combinator
if (Expr.relative[(type = token.type)]) {
break;
}
//find查找器有ID,TAG,NAME,CLASS,都是對應原生API,比如div:not(.aaa),div就優先被處理了
if ((find = Expr.find[type])) {
//如果tokens[0].type為關系選擇器,則往上找一級,用其父節點作上下文
if ((seed = find(
token.matches[0].replace(runescape, funescape),
rsibling.test(tokens[0].type) && context.parentNode || context))) {
//然后去掉用過的選擇器,比如上例中的div
tokens.splice(i, 1);
selector = seed.length && toSelector(tokens);
if (!selector) {//如果選擇符為空白,那么將種子集合並到結構集中
push.apply(results, seed);
return results;
}
break;
}
}
}
}
}
// Compile and execute a filtering function
// Provide `match` to avoid retokenization if we modified the selector above
compile(selector, match)(
seed,
context, !documentIsHTML,
results,
rsibling.test(selector));
return results;
}
// Deprecated
Expr.pseudos["nth"] = Expr.pseudos["eq"];
// Easy API for creating new setFilters
function setFilters() {}
setFilters.prototype = Expr.filters = Expr.pseudos;
Expr.setFilters = new setFilters();
//判定穩定性
//http://www.iteye.com/topic/714688
// Array.prototype.sort在不同瀏覽器中表現可能不一致。
//var arr =[{id:1, value:'a'},{id:1, value:'b'},{id:1, value:'c'}];
//var arr = arr.sort(function(a,b){return b.id-a.id});
//for(var n=0,m=arr.length;n<m;n++){
// alert(arr[n].value);
//}
//以上代碼在Chrome執行，將得到c,b,a。
//而在其他瀏覽器(IE6/7/8,FF3,Opera10,Safari5)中，得到a,b,c。
//不強制參與排序的元素保持原來的順序（可以不穩定）。實際上Chrome對比較后相等的元素進行了交換操作，而其他的JS引擎沒有這么做。
support.sortStable = expando.split("").sort(sortOrder).join("") === expando;
// Initialize with the default document
setDocument();
// Always assume the presence of duplicates if sort doesn't
// pass them to our comparison function (as in Google Chrome).
[0, 0].sort(sortOrder);
support.detectDuplicates = hasDuplicate;
// EXPOSE
if (typeof define === "function" && define.amd) {
define(function() {
return Sizzle;
});
} else {
window.Sizzle = Sizzle;
}
// EXPOSE
})(window);