jQuery中选择器引擎Sizzle的解析

[
 [
 { "value": "p", "type": "TAG", "matches": ["p"] }, 
 { "value": ".cls", "type": "CLASS", "matches": ["cls"] }, 
 { "value": " ", "type": " " }, 
 { "value": "input", "type": "TAG", "matches": ["input"] }, 
 { "value": "[type=\"text\"]", "type": "ATTR", "matches": ["type", "=", "text"]}
 ]
]

// 这个matcherFromTokens中这个for循环，之前讲过了，但是 有个地方我们跳过没讲
for ( ; i < len; i++ ) {
 if ( (matcher = Expr.relative[ tokens[i].type ]) ) {
 matchers = [ addCombinator(elementMatcher( matchers ), matcher) ];
 } else {
 matcher = Expr.filter[ tokens[i].type ].apply( null, tokens[i].matches );

 // Return special upon seeing a positional matcher
 // 这个就是处理位置伪类的逻辑
 if ( matcher[ expando ] ) {
 // Find the next relative operator (if any) for proper handling
 j = ++i;
 for ( ; j < len; j++ ) { // 寻找下一个关系节点位置，并用j记录下来
 if ( Expr.relative[ tokens[j].type ] ) {
 break;
 }
 }
 return setMatcher(// setMatcher 是生成位置伪类查询的工厂方法
 i > 1 && elementMatcher( matchers ), // 位置伪类之前的matcher
 i > 1 && toSelector(
 // If the preceding token was a descendant combinator, insert an implicit any-element `*`
 tokens.slice( 0, i - 1 ).concat({ value: tokens[ i - 2 ].type === " " ? "*" : "" })
 ).replace( rtrim, "$1" ), // 位置伪类之前的selector
 matcher, // 位置伪类本身的matcher
 i < j && matcherFromTokens( tokens.slice( i, j ) ), // 位置伪类本身的filter
 j < len && matcherFromTokens( (tokens = tokens.slice( j )) ), // 位置伪类之后的matcher
 j < len && toSelector( tokens ) // 位置伪类之后的selector
 );
 }
 matchers.push( matcher );
 }
 }

//第1个参数，preFilter，前置过滤器，相当于伪类token之前`.mark li.limark`的过滤器matcher
//第2个参数，selector，伪类之前的selector (`.mark li.limark`)
//第3个参数，matcher， 当前位置伪类的过滤器matcher `:first`
//第4个参数，postFilter，伪类之后的过滤器 `.limark2`
//第5个参数，postFinder，后置搜索器，相当于在前边过滤出来的集合里边再搜索剩下的规则的一个搜索器 ` a span`的matcher
//第6个参数，postSelector，后置搜索器对应的选择器字符串，相当于` a span`
function setMatcher( preFilter, selector, matcher, postFilter, postFinder, postSelector ) {
 //TODO: setMatcher 会把这俩货在搞一次setMatcher， 还不太懂
 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 ) {
 // 这个就是 匹配位置伪类的 逻辑， 将符合位置伪类的节点剔出来
 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( 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 );
 }
 }
 });
}