教你实现 jQuery 的选择器
做网站免不了用到JS，如果大量用到选择一个JS框架是个不错的选择，今天我就抛砖引玉说说jQuery的选择器，了解它的原理是提高效率的最佳途径。每当你看到jQuery独特的语法时是否有想过它是如何实现的呢？是否觉得相当复杂让你都不敢去想呢，今天就让我们揭开jQuery选择器的神秘面纱。
一、选择器入口
var Utils = {
find : function (expr,context){
return selector.quick(expr,context || document);
}
}
find : function (expr,context){
return selector.quick(expr,context || document);
}
}
expr就是表达式了，如下(注：我所说的都是jQuery的原理)：
代码
//效率最高，直接映射到document.getElementById
Utils.find("#id")
//支持querySelectorAll否则调用context.getElementsByName然后遍历getAttribute("name")等于a的
Utils.find("input[name=a]")
//不支持querySelectorAll，调用context.getElementsByName然后遍历getAttribute("name")等于a的,然后筛选出选中的
Utils.find("input:checked[name=a]")
//支持querySelectorAll否则映射到context.getElementsByTagName
Utils.find("input")
//支持querySelectorAll否则调用context.getElementsByTagName("*")然后筛选出className包含className的标签
Utils.find(".cssName")
Utils.find("#id")
//支持querySelectorAll否则调用context.getElementsByName然后遍历getAttribute("name")等于a的
Utils.find("input[name=a]")
//不支持querySelectorAll，调用context.getElementsByName然后遍历getAttribute("name")等于a的,然后筛选出选中的
Utils.find("input:checked[name=a]")
//支持querySelectorAll否则映射到context.getElementsByTagName
Utils.find("input")
//支持querySelectorAll否则调用context.getElementsByTagName("*")然后筛选出className包含className的标签
Utils.find(".cssName")
context 上下文哦，主要是在这个里面查找哦
代码
var selector = {};
selector.quick = function(expr,context){
//#id
if( /^#([\w-]+)$/.test( expr ) ){
return context.getElementById( expr.substr(1) );
}
//TAG
else if ( /^\w+$/.test( expr ) ) {
return selector.array( context.getElementsByTagName( expr ));
}
try
{
return selector.array(context.querySelectorAll(expr));//ie6 ie7都不支持哦
}catch(e) {}
return selector.array(selector(expr,context,isXML(context)));//不支持就只能用最原始的啦
}
selector.quick = function(expr,context){
//#id
if( /^#([\w-]+)$/.test( expr ) ){
return context.getElementById( expr.substr(1) );
}
//TAG
else if ( /^\w+$/.test( expr ) ) {
return selector.array( context.getElementsByTagName( expr ));
}
try
{
return selector.array(context.querySelectorAll(expr));//ie6 ie7都不支持哦
}catch(e) {}
return selector.array(selector(expr,context,isXML(context)));//不支持就只能用最原始的啦
}
querySelectorAll 是什么？这个可是主角啊，jQuery独特的语法其实就是参考自它的，标准且主流的浏览器都支持了，比如ie8，ff等等，然而ie6、ie7都不支持哦，所以我们需要自己来实现，后面很多代码其实都是为了解决不支持它而写的，可恨啊。。。
查看资料：
http://www.w3.org/TR/selectors-api/
http://www.w3.org/TR/css3-selectors/
http://msdn.microsoft.com/zh-cn/library/cc304114(en-us,VS.85).aspx
看看document.querySelectorAll都支持什么语法
代码
var a = document.querySelectorAll("#a, #b, #c");
var b = document.querySelectorAll("#frm p #a");
var c = document.querySelectorAll("body p.cssName");
var d = document.querySelectorAll("p.abc, #a");
var e = document.querySelectorAll("input");
var f = document.querySelector("body p[id=aa] span");
var g = document.querySelectorAll("ul.nav>li");
var h = document.querySelectorAll("input[checked=checked]");
//.....
var b = document.querySelectorAll("#frm p #a");
var c = document.querySelectorAll("body p.cssName");
var d = document.querySelectorAll("p.abc, #a");
var e = document.querySelectorAll("input");
var f = document.querySelector("body p[id=aa] span");
var g = document.querySelectorAll("ul.nav>li");
var h = document.querySelectorAll("input[checked=checked]");
//.....
二、选择器实现
代码
var selector = function(expr, context, isXML){
var set, match;
if ( !expr ) {
return [];
}
for ( var i = 0, l = Expr.order.length; i < l; i++ ) {
var type = Expr.order[i], match;
if ( (match = Expr.leftMatch[ type ].exec( expr )) ) {
var left = match[1];
match.splice(1,1);
if ( left.substr( left.length - 1 ) !== "\\" ) {
match[1] = (match[1] || "").replace(/\\/g, "");
set = Expr.find[ type ]( match, context, isXML );
if ( set != null ) {
expr = expr.replace( Expr.match[ type ], "" );
break;
}
}
}
}
if ( !set ) {
set = context.getElementsByTagName("*");//效率非常低下，获取所有的标签，然后调用filter筛选出需要的
}
return filter(expr,set);
};
selector.array = function(array){
var ret = [];
if ( Object.prototype.toString.call(array) === "[object Array]" ) {
Array.prototype.push.apply( ret, array );
} else {
if ( typeof array.length === "number" ) {
for ( var i = 0, l = array.length; i < l; i++ ) {
ret.push( array[i] );
}
} else {
for ( var i = 0; array[i]; i++ ) {
ret.push( array[i] );
}
}
}
return ret;
}
//判断是否是xml
var 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 : 0).documentElement;
return documentElement ? documentElement.nodeName !== "HTML" : false;
};
var set, match;
if ( !expr ) {
return [];
}
for ( var i = 0, l = Expr.order.length; i < l; i++ ) {
var type = Expr.order[i], match;
if ( (match = Expr.leftMatch[ type ].exec( expr )) ) {
var left = match[1];
match.splice(1,1);
if ( left.substr( left.length - 1 ) !== "\\" ) {
match[1] = (match[1] || "").replace(/\\/g, "");
set = Expr.find[ type ]( match, context, isXML );
if ( set != null ) {
expr = expr.replace( Expr.match[ type ], "" );
break;
}
}
}
}
if ( !set ) {
set = context.getElementsByTagName("*");//效率非常低下，获取所有的标签，然后调用filter筛选出需要的
}
return filter(expr,set);
};
selector.array = function(array){
var ret = [];
if ( Object.prototype.toString.call(array) === "[object Array]" ) {
Array.prototype.push.apply( ret, array );
} else {
if ( typeof array.length === "number" ) {
for ( var i = 0, l = array.length; i < l; i++ ) {
ret.push( array[i] );
}
} else {
for ( var i = 0; array[i]; i++ ) {
ret.push( array[i] );
}
}
}
return ret;
}
//判断是否是xml
var 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 : 0).documentElement;
return documentElement ? documentElement.nodeName !== "HTML" : false;
};
其实上面都实现大半了，下面会有很多代码其实都是为了解决不支持querySelectorAll 而写的。看代码吧，其实不难。
代码
var Expr = {
order: [ "ID", "NAME", "TAG" ],
match: {
ID: /#((?:[\w\u00c0-\uFFFF-]|\\.)+)/,
CLASS: /\.((?:[\w\u00c0-\uFFFF-]|\\.)+)/,
NAME: /\[name=['"]*((?:[\w\u00c0-\uFFFF-]|\\.)+)['"]*\]/,
ATTR: /\[\s*((?:[\w\u00c0-\uFFFF-]|\\.)+)\s*(?:(\S?=)\s*(['"]*)(.*?)\3|)\s*\]/,
TAG: /^((?:[\w\u00c0-\uFFFF\*-]|\\.)+)/,
CHILD: /:(only|nth|last|first)-child(?:\((even|odd|[\dn+-]*)\))?/,
POS: /:(nth|eq|gt|lt|first|last|even|odd)(?:\((\d*)\))?(?=[^-]|$)/,
PSEUDO: /:((?:[\w\u00c0-\uFFFF-]|\\.)+)(?:\((['"]?)((?:\([^\)]+\)|[^\(\)]*)+)\2\))?/
},
leftMatch: {},
attrMap: {
"class": "className",
"for": "htmlFor"
},
attrHandle: {
href: function(elem){
return elem.getAttribute("href");
}
},
relative: {
"+": function(checkSet, part){
var isPartStr = typeof part === "string",
isTag = isPartStr && !/\W/.test(part),
isPartStrNotTag = isPartStr && !isTag;
if ( isTag ) {
part = part.toLowerCase();
}
for ( var i = 0, l = checkSet.length, elem; i < l; i++ ) {
if ( (elem = checkSet[i]) ) {
while ( (elem = elem.previousSibling) && elem.nodeType !== 1 ) {}
checkSet[i] = isPartStrNotTag || elem && elem.nodeName.toLowerCase() === part ?
elem || false :
elem === part;
}
}
if ( isPartStrNotTag ) {
Sizzle.filter( part, checkSet, true );
}
},
">": function(checkSet, part){
var isPartStr = typeof part === "string";
if ( isPartStr && !/\W/.test(part) ) {
part = part.toLowerCase();
for ( var i = 0, l = checkSet.length; i < l; i++ ) {
var elem = checkSet[i];
if ( elem ) {
var parent = elem.parentNode;
checkSet[i] = parent.nodeName.toLowerCase() === part ? parent : false;
}
}
} else {
for ( var i = 0, l = checkSet.length; i < l; i++ ) {
var elem = checkSet[i];
if ( elem ) {
checkSet[i] = isPartStr ?
elem.parentNode :
elem.parentNode === part;
}
}
if ( isPartStr ) {
Sizzle.filter( part, checkSet, true );
}
}
},
"": function(checkSet, part, isXML){
var doneName = done++, checkFn = dirCheck;
if ( typeof part === "string" && !/\W/.test(part) ) {
var nodeCheck = part = part.toLowerCase();
checkFn = dirNodeCheck;
}
checkFn("parentNode", part, doneName, checkSet, nodeCheck, isXML);
},
"~": function(checkSet, part, isXML){
var doneName = done++, checkFn = dirCheck;
if ( typeof part === "string" && !/\W/.test(part) ) {
var nodeCheck = part = part.toLowerCase();
checkFn = dirNodeCheck;
}
checkFn("previousSibling", part, doneName, checkSet, nodeCheck, isXML);
}
},
find: {
ID: function(match, context, isXML){
if ( typeof context.getElementById !== "undefined" && !isXML ) {
var m = context.getElementById(match[1]);
return m ? [m] : [];
}
},
NAME: function(match, context){
if ( typeof context.getElementsByName !== "undefined" ) {
var ret = [], results = context.getElementsByName(match[1]);
for ( var i = 0, l = results.length; i < l; i++ ) {
if ( results[i].getAttribute("name") === match[1] ) {
ret.push( results[i] );
}
}
return ret.length === 0 ? null : ret;
}
},
TAG: function(match, context){
return context.getElementsByTagName(match[1]);
}
},
preFilter: {
CLASS: function(match, curLoop, inplace, result, not, isXML){
match = " " + match[1].replace(/\\/g, "") + " ";
if ( isXML ) {
return match;
}
for ( var i = 0, elem; (elem = curLoop[i]) != null; i++ ) {
if ( elem ) {
if ( not ^ (elem.className && (" " + elem.className + " ").replace(/[\t\n]/g, " ").indexOf(match) >= 0) ) {
if ( !inplace ) {
result.push( elem );
}
} else if ( inplace ) {
curLoop[i] = false;
}
}
}
return false;
},
ID: function(match){
return match[1].replace(/\\/g, "");
},
TAG: function(match, curLoop){
return match[1].toLowerCase();
},
CHILD: function(match){
if ( match[1] === "nth" ) {
// parse equations like 'even', 'odd', '5', '2n', '3n+2', '4n-1', '-n+6'
var test = /(-?)(\d*)n((?:\+|-)?\d*)/.exec(
match[2] === "even" && "2n" || match[2] === "odd" && "2n+1" ||
!/\D/.test( match[2] ) && "0n+" + match[2] || match[2]);
// calculate the numbers (first)n+(last) including if they are negative
match[2] = (test[1] + (test[2] || 1)) - 0;
match[3] = test[3] - 0;
}
// TODO: Move to normal caching system
match[0] = done++;
return match;
},
ATTR: function(match, curLoop, inplace, result, not, isXML){
var name = match[1].replace(/\\/g, "");
if ( !isXML && Expr.attrMap[name] ) {
match[1] = Expr.attrMap[name];
}
if ( match[2] === "~=" ) {
match[4] = " " + match[4] + " ";
}
return match;
},
PSEUDO: function(match, curLoop, inplace, result, not){
if ( match[1] === "not" ) {
// If we're dealing with a complex expression, or a simple one
if ( ( chunker.exec(match[3]) || "" ).length > 1 || /^\w/.test(match[3]) ) {
match[3] = Sizzle(match[3], null, null, curLoop);
} else {
var ret = Sizzle.filter(match[3], curLoop, inplace, true ^ not);
if ( !inplace ) {
result.push.apply( result, ret );
}
return false;
}
} else if ( Expr.match.POS.test( match[0] ) || Expr.match.CHILD.test( match[0] ) ) {
return true;
}
return match;
},
POS: function(match){
match.unshift( true );
return match;
}
},
filters: {
enabled: function(elem){
return elem.disabled === false && elem.type !== "hidden";
},
disabled: function(elem){
return elem.disabled === true;
},
checked: function(elem){
return elem.checked === true;
},
selected: function(elem){
// Accessing this property makes selected-by-default
// options in Safari work properly
elem.parentNode.selectedIndex;
return elem.selected === true;
},
parent: function(elem){
return !!elem.firstChild;
},
empty: function(elem){
return !elem.firstChild;
},
has: function(elem, i, match){
return !!Sizzle( match[3], elem ).length;
},
header: function(elem){
return /h\d/i.test( elem.nodeName );
},
text: function(elem){
return "text" === elem.type;
},
radio: function(elem){
return "radio" === elem.type;
},
checkbox: function(elem){
return "checkbox" === elem.type;
},
file: function(elem){
return "file" === elem.type;
},
password: function(elem){
return "password" === elem.type;
},
submit: function(elem){
return "submit" === elem.type;
},
image: function(elem){
return "image" === elem.type;
},
reset: function(elem){
return "reset" === elem.type;
},
button: function(elem){
return "button" === elem.type || elem.nodeName.toLowerCase() === "button";
},
input: function(elem){
return /input|select|textarea|button/i.test(elem.nodeName);
}
},
setFilters: {
first: function(elem, i){
return i === 0;
},
last: function(elem, i, match, array){
return i === array.length - 1;
},
even: function(elem, i){
return i % 2 === 0;
},
odd: function(elem, i){
return i % 2 === 1;
},
lt: function(elem, i, match){
return i < match[3] - 0;
},
gt: function(elem, i, match){
return i > match[3] - 0;
},
nth: function(elem, i, match){
return match[3] - 0 === i;
},
eq: function(elem, i, match){
return match[3] - 0 === i;
}
},
filter: {
PSEUDO: function(elem, match, i, array){
var name = match[1], filter = Expr.filters[ name ];
if ( filter ) {
return filter( elem, i, match, array );
} else if ( name === "contains" ) {
return (elem.textContent || elem.innerText || getText([ elem ]) || "").indexOf(match[3]) >= 0;
} else if ( name === "not" ) {
var not = match[3];
for ( var i = 0, l = not.length; i < l; i++ ) {
if ( not[i] === elem ) {
return false;
}
}
return true;
} else {
Sizzle.error( "Syntax error, unrecognized expression: " + name );
}
},
CHILD: function(elem, match){
var type = match[1], node = elem;
switch (type) {
case 'only':
case 'first':
while ( (node = node.previousSibling) ) {
if ( node.nodeType === 1 ) {
return false;
}
}
if ( type === "first" ) {
return true;
}
node = elem;
case 'last':
while ( (node = node.nextSibling) ) {
if ( node.nodeType === 1 ) {
return false;
}
}
return true;
case 'nth':
var first = match[2], last = match[3];
if ( first === 1 && last === 0 ) {
return true;
}
var doneName = match[0],
parent = elem.parentNode;
if ( parent && (parent.sizcache !== doneName || !elem.nodeIndex) ) {
var count = 0;
for ( node = parent.firstChild; node; node = node.nextSibling ) {
if ( node.nodeType === 1 ) {
node.nodeIndex = ++count;
}
}
parent.sizcache = doneName;
}
var diff = elem.nodeIndex - last;
if ( first === 0 ) {
return diff === 0;
} else {
return ( diff % first === 0 && diff / first >= 0 );
}
}
},
ID: function(elem, match){
return elem.nodeType === 1 && elem.getAttribute("id") === match;
},
TAG: function(elem, match){
return (match === "*" && elem.nodeType === 1) || elem.nodeName.toLowerCase() === match;
},
CLASS: function(elem, match){
return (" " + (elem.className || elem.getAttribute("class")) + " ")
.indexOf( match ) > -1;
},
ATTR: function(elem, match){
var name = match[1],
result = Expr.attrHandle[ name ] ?
Expr.attrHandle[ name ]( elem ) :
elem[ name ] != null ?
elem[ name ] :
elem.getAttribute( name ),
value = result + "",
type = match[2],
check = match[4];
return result == null ?
type === "!=" :
type === "=" ?
value === check :
type === "*=" ?
value.indexOf(check) >= 0 :
type === "~=" ?
(" " + value + " ").indexOf(check) >= 0 :
!check ?
value && result !== false :
type === "!=" ?
value !== check :
type === "^=" ?
value.indexOf(check) === 0 :
type === "$=" ?
value.substr(value.length - check.length) === check :
type === "|=" ?
value === check || value.substr(0, check.length + 1) === check + "-" :
false;
},
POS: function(elem, match, i, array){
var name = match[2], filter = Expr.setFilters[ name ];
if ( filter ) {
return filter( elem, i, match, array );
}
}
}
};
for ( var type in Expr.match ) {
Expr.match[ type ] = new RegExp( Expr.match[ type ].source + /(?![^\[]*\])(?![^\(]*\))/.source );
Expr.leftMatch[ type ] = new RegExp( /(^(?:.|\r|\n)*?)/.source + Expr.match[ type ].source.replace(/\\(\d+)/g, function(all, num){
return "\\" + (num - 0 + 1);
}));
}
order: [ "ID", "NAME", "TAG" ],
match: {
ID: /#((?:[\w\u00c0-\uFFFF-]|\\.)+)/,
CLASS: /\.((?:[\w\u00c0-\uFFFF-]|\\.)+)/,
NAME: /\[name=['"]*((?:[\w\u00c0-\uFFFF-]|\\.)+)['"]*\]/,
ATTR: /\[\s*((?:[\w\u00c0-\uFFFF-]|\\.)+)\s*(?:(\S?=)\s*(['"]*)(.*?)\3|)\s*\]/,
TAG: /^((?:[\w\u00c0-\uFFFF\*-]|\\.)+)/,
CHILD: /:(only|nth|last|first)-child(?:\((even|odd|[\dn+-]*)\))?/,
POS: /:(nth|eq|gt|lt|first|last|even|odd)(?:\((\d*)\))?(?=[^-]|$)/,
PSEUDO: /:((?:[\w\u00c0-\uFFFF-]|\\.)+)(?:\((['"]?)((?:\([^\)]+\)|[^\(\)]*)+)\2\))?/
},
leftMatch: {},
attrMap: {
"class": "className",
"for": "htmlFor"
},
attrHandle: {
href: function(elem){
return elem.getAttribute("href");
}
},
relative: {
"+": function(checkSet, part){
var isPartStr = typeof part === "string",
isTag = isPartStr && !/\W/.test(part),
isPartStrNotTag = isPartStr && !isTag;
if ( isTag ) {
part = part.toLowerCase();
}
for ( var i = 0, l = checkSet.length, elem; i < l; i++ ) {
if ( (elem = checkSet[i]) ) {
while ( (elem = elem.previousSibling) && elem.nodeType !== 1 ) {}
checkSet[i] = isPartStrNotTag || elem && elem.nodeName.toLowerCase() === part ?
elem || false :
elem === part;
}
}
if ( isPartStrNotTag ) {
Sizzle.filter( part, checkSet, true );
}
},
">": function(checkSet, part){
var isPartStr = typeof part === "string";
if ( isPartStr && !/\W/.test(part) ) {
part = part.toLowerCase();
for ( var i = 0, l = checkSet.length; i < l; i++ ) {
var elem = checkSet[i];
if ( elem ) {
var parent = elem.parentNode;
checkSet[i] = parent.nodeName.toLowerCase() === part ? parent : false;
}
}
} else {
for ( var i = 0, l = checkSet.length; i < l; i++ ) {
var elem = checkSet[i];
if ( elem ) {
checkSet[i] = isPartStr ?
elem.parentNode :
elem.parentNode === part;
}
}
if ( isPartStr ) {
Sizzle.filter( part, checkSet, true );
}
}
},
"": function(checkSet, part, isXML){
var doneName = done++, checkFn = dirCheck;
if ( typeof part === "string" && !/\W/.test(part) ) {
var nodeCheck = part = part.toLowerCase();
checkFn = dirNodeCheck;
}
checkFn("parentNode", part, doneName, checkSet, nodeCheck, isXML);
},
"~": function(checkSet, part, isXML){
var doneName = done++, checkFn = dirCheck;
if ( typeof part === "string" && !/\W/.test(part) ) {
var nodeCheck = part = part.toLowerCase();
checkFn = dirNodeCheck;
}
checkFn("previousSibling", part, doneName, checkSet, nodeCheck, isXML);
}
},
find: {
ID: function(match, context, isXML){
if ( typeof context.getElementById !== "undefined" && !isXML ) {
var m = context.getElementById(match[1]);
return m ? [m] : [];
}
},
NAME: function(match, context){
if ( typeof context.getElementsByName !== "undefined" ) {
var ret = [], results = context.getElementsByName(match[1]);
for ( var i = 0, l = results.length; i < l; i++ ) {
if ( results[i].getAttribute("name") === match[1] ) {
ret.push( results[i] );
}
}
return ret.length === 0 ? null : ret;
}
},
TAG: function(match, context){
return context.getElementsByTagName(match[1]);
}
},
preFilter: {
CLASS: function(match, curLoop, inplace, result, not, isXML){
match = " " + match[1].replace(/\\/g, "") + " ";
if ( isXML ) {
return match;
}
for ( var i = 0, elem; (elem = curLoop[i]) != null; i++ ) {
if ( elem ) {
if ( not ^ (elem.className && (" " + elem.className + " ").replace(/[\t\n]/g, " ").indexOf(match) >= 0) ) {
if ( !inplace ) {
result.push( elem );
}
} else if ( inplace ) {
curLoop[i] = false;
}
}
}
return false;
},
ID: function(match){
return match[1].replace(/\\/g, "");
},
TAG: function(match, curLoop){
return match[1].toLowerCase();
},
CHILD: function(match){
if ( match[1] === "nth" ) {
// parse equations like 'even', 'odd', '5', '2n', '3n+2', '4n-1', '-n+6'
var test = /(-?)(\d*)n((?:\+|-)?\d*)/.exec(
match[2] === "even" && "2n" || match[2] === "odd" && "2n+1" ||
!/\D/.test( match[2] ) && "0n+" + match[2] || match[2]);
// calculate the numbers (first)n+(last) including if they are negative
match[2] = (test[1] + (test[2] || 1)) - 0;
match[3] = test[3] - 0;
}
// TODO: Move to normal caching system
match[0] = done++;
return match;
},
ATTR: function(match, curLoop, inplace, result, not, isXML){
var name = match[1].replace(/\\/g, "");
if ( !isXML && Expr.attrMap[name] ) {
match[1] = Expr.attrMap[name];
}
if ( match[2] === "~=" ) {
match[4] = " " + match[4] + " ";
}
return match;
},
PSEUDO: function(match, curLoop, inplace, result, not){
if ( match[1] === "not" ) {
// If we're dealing with a complex expression, or a simple one
if ( ( chunker.exec(match[3]) || "" ).length > 1 || /^\w/.test(match[3]) ) {
match[3] = Sizzle(match[3], null, null, curLoop);
} else {
var ret = Sizzle.filter(match[3], curLoop, inplace, true ^ not);
if ( !inplace ) {
result.push.apply( result, ret );
}
return false;
}
} else if ( Expr.match.POS.test( match[0] ) || Expr.match.CHILD.test( match[0] ) ) {
return true;
}
return match;
},
POS: function(match){
match.unshift( true );
return match;
}
},
filters: {
enabled: function(elem){
return elem.disabled === false && elem.type !== "hidden";
},
disabled: function(elem){
return elem.disabled === true;
},
checked: function(elem){
return elem.checked === true;
},
selected: function(elem){
// Accessing this property makes selected-by-default
// options in Safari work properly
elem.parentNode.selectedIndex;
return elem.selected === true;
},
parent: function(elem){
return !!elem.firstChild;
},
empty: function(elem){
return !elem.firstChild;
},
has: function(elem, i, match){
return !!Sizzle( match[3], elem ).length;
},
header: function(elem){
return /h\d/i.test( elem.nodeName );
},
text: function(elem){
return "text" === elem.type;
},
radio: function(elem){
return "radio" === elem.type;
},
checkbox: function(elem){
return "checkbox" === elem.type;
},
file: function(elem){
return "file" === elem.type;
},
password: function(elem){
return "password" === elem.type;
},
submit: function(elem){
return "submit" === elem.type;
},
image: function(elem){
return "image" === elem.type;
},
reset: function(elem){
return "reset" === elem.type;
},
button: function(elem){
return "button" === elem.type || elem.nodeName.toLowerCase() === "button";
},
input: function(elem){
return /input|select|textarea|button/i.test(elem.nodeName);
}
},
setFilters: {
first: function(elem, i){
return i === 0;
},
last: function(elem, i, match, array){
return i === array.length - 1;
},
even: function(elem, i){
return i % 2 === 0;
},
odd: function(elem, i){
return i % 2 === 1;
},
lt: function(elem, i, match){
return i < match[3] - 0;
},
gt: function(elem, i, match){
return i > match[3] - 0;
},
nth: function(elem, i, match){
return match[3] - 0 === i;
},
eq: function(elem, i, match){
return match[3] - 0 === i;
}
},
filter: {
PSEUDO: function(elem, match, i, array){
var name = match[1], filter = Expr.filters[ name ];
if ( filter ) {
return filter( elem, i, match, array );
} else if ( name === "contains" ) {
return (elem.textContent || elem.innerText || getText([ elem ]) || "").indexOf(match[3]) >= 0;
} else if ( name === "not" ) {
var not = match[3];
for ( var i = 0, l = not.length; i < l; i++ ) {
if ( not[i] === elem ) {
return false;
}
}
return true;
} else {
Sizzle.error( "Syntax error, unrecognized expression: " + name );
}
},
CHILD: function(elem, match){
var type = match[1], node = elem;
switch (type) {
case 'only':
case 'first':
while ( (node = node.previousSibling) ) {
if ( node.nodeType === 1 ) {
return false;
}
}
if ( type === "first" ) {
return true;
}
node = elem;
case 'last':
while ( (node = node.nextSibling) ) {
if ( node.nodeType === 1 ) {
return false;
}
}
return true;
case 'nth':
var first = match[2], last = match[3];
if ( first === 1 && last === 0 ) {
return true;
}
var doneName = match[0],
parent = elem.parentNode;
if ( parent && (parent.sizcache !== doneName || !elem.nodeIndex) ) {
var count = 0;
for ( node = parent.firstChild; node; node = node.nextSibling ) {
if ( node.nodeType === 1 ) {
node.nodeIndex = ++count;
}
}
parent.sizcache = doneName;
}
var diff = elem.nodeIndex - last;
if ( first === 0 ) {
return diff === 0;
} else {
return ( diff % first === 0 && diff / first >= 0 );
}
}
},
ID: function(elem, match){
return elem.nodeType === 1 && elem.getAttribute("id") === match;
},
TAG: function(elem, match){
return (match === "*" && elem.nodeType === 1) || elem.nodeName.toLowerCase() === match;
},
CLASS: function(elem, match){
return (" " + (elem.className || elem.getAttribute("class")) + " ")
.indexOf( match ) > -1;
},
ATTR: function(elem, match){
var name = match[1],
result = Expr.attrHandle[ name ] ?
Expr.attrHandle[ name ]( elem ) :
elem[ name ] != null ?
elem[ name ] :
elem.getAttribute( name ),
value = result + "",
type = match[2],
check = match[4];
return result == null ?
type === "!=" :
type === "=" ?
value === check :
type === "*=" ?
value.indexOf(check) >= 0 :
type === "~=" ?
(" " + value + " ").indexOf(check) >= 0 :
!check ?
value && result !== false :
type === "!=" ?
value !== check :
type === "^=" ?
value.indexOf(check) === 0 :
type === "$=" ?
value.substr(value.length - check.length) === check :
type === "|=" ?
value === check || value.substr(0, check.length + 1) === check + "-" :
false;
},
POS: function(elem, match, i, array){
var name = match[2], filter = Expr.setFilters[ name ];
if ( filter ) {
return filter( elem, i, match, array );
}
}
}
};
for ( var type in Expr.match ) {
Expr.match[ type ] = new RegExp( Expr.match[ type ].source + /(?![^\[]*\])(?![^\(]*\))/.source );
Expr.leftMatch[ type ] = new RegExp( /(^(?:.|\r|\n)*?)/.source + Expr.match[ type ].source.replace(/\\(\d+)/g, function(all, num){
return "\\" + (num - 0 + 1);
}));
}
jQuery 不是获取的多个元素可以each遍历么？看看如何实现哦
代码
if (!Object.prototype.each) {
Array.prototype.each = function (fn) {
if ( this.length > 0 ) {
for ( var i = 0; i < this.length; i++ ) {
fn.call( this[i], i );
}
}
}
}
Array.prototype.each = function (fn) {
if ( this.length > 0 ) {
for ( var i = 0; i < this.length; i++ ) {
fn.call( this[i], i );
}
}
}
}
