for ( type in Expr.filter ) {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 );}}

preFilter: {//match是捕获组//如果：[arr^='val']"ATTR": function( match ) {//attr的第一个捕获 组是arr,将当中的转码变成原来的字符match[1] = match[1].replace( runescape, funescape );// Move the given value to match[3] whether quoted or unquoted// 将val放到捕获组3里，原来的捕获组3捕获'或"match[3] = ( match[4] || match[5] || "" ).replace( runescape, funescape );//如果捕获组2是~=。在match[3]前后加空格,以方便匹配单个单词if ( match[2] === "~=" ) {match[3] = " " + match[3] + " ";}//match[0] = '[arr^='val']'//match[1] = 'arr'//match[2] = '='//match[3] = '111'return match.slice( 0, 4 );},"CHILD": function( match ) {/*  比如nth-child(-2n+1)的捕获组mathc[1] nthmathc[2] childmathc[3] 2n+1mathc[4] 2nmathc[5] -mathc[6] 2mathc[7] +mathc[8] 1*/match[1] = match[1].toLowerCase();// nth必须须要參数if ( match[1].slice( 0, 3 ) === "nth" ) {// nth-* requires argumentif ( !match[3] ) {Sizzle.error( match[0] );}// numeric x and y parameters for Expr.filter.CHILD// remember that false/true cast respectively to 0/1// xn + y// 将even,odd修正为xn+y,match[4]修正为+-xmatch[4] = +( match[4] ? match[5] + (match[6] || 1) : 2 * ( match[3] === "even" || match[3] === "odd" ) );// 将match[5]替换为+-ymatch[5] = +( ( match[7] + match[8] ) || match[3] === "odd" );// other types prohibit arguments// 除nth外其它类型禁止參数} else if ( match[3] ) {Sizzle.error( match[0] );}// match[0] :nth-child(-2n+1)// match[1] nth// match[2] child// match[3] -2n+1// match[4] -2// match[5] 1// match[6] 2// match[7] +// match[8] 1return match;},/*** match[1] :后伪类类型* match[2] 伪类參数* match[3] 參数中的'或者"* match[4] 除去'或"的伪类*/"PSEUDO": function( match ) {var excess,unquoted = !match[5] && match[2];//是CHILD伪类。返回nullif ( matchExpr[ "CHILD"].test( match[0] ) ) {return null;}// Accept quoted arguments as-is// 參数有引號//将match[2]替换为无引號的match[4]參数if ( match[3] && match[4] !== undefined ) {match[2] = match[4];// Strip excess characters from unquoted arguments// 除去带引號的參数的多余字符} else if ( unquoted && rpseudo.test( unquoted ) &&// Get excess from tokenize (recursively)//excess多余字符的长度(excess = tokenize( unquoted, true )) &&//excess多余參数的索引位置,excess是个负值,以便截取到多余字符之前(excess = unquoted.indexOf( ")", unquoted.length - excess ) - unquoted.length) ) {// excess is a negative indexmatch[0] = match[0].slice( 0, excess );match[2] = unquoted.slice( 0, excess );}// Return only captures needed by the pseudo filter method (type and argument)return match.slice( 0, 3 );}}