jquery Selector code in detail (iv)--expr.prefilter

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Expr.prefilter is a method for preprocessing attr, child, pseudo three selectors in the Tokenize method. Specific as follows:

Expr.prefilter: {"ATTR": function (Match) {/* * * Complete the following tasks: * 1, property name decoding * 2, attribute value decoding * 3, if the judgment is ~=, then add a space * 4 to the property value, return the final Mtach object *     * Match[1] denotes the property name, * Match[1].replace (RuneScape, Funescape): Decodes the hexadecimal number in the property name to * Single-byte Unicode characters or double-byte Unicode characters (Chinese or other text that requires two-byte expression) * Detailed descriptions of regular expressions can be see my "detailed jquery selector regular expression" article */match[1] = Match[1].replace (  RuneScape, funescape);/* Decode attribute value * Match[4]: denotes attribute value placed in single or double quotation marks * Match[5]: denotes attribute values not enclosed in quotation marks */match[3] = (Match[4] | | | match[5] || ""). Replace (runescape,funescape);/* ~= means word match, the definition of words in the "word" is blank for different words of the delimiter * so in match[3] on both sides with a space, you can use IndexOf, Correctly identify if the word exists */if (match[2] = = = "~=") {match[3] = "+ match[3] +" ";} /* * Returns useful first four element results */return match.slice (0, 4);}, "Child": function (Match) {/* * * * Complete several tasks: * 1, change the character before child and Of-type in the command to lowercase characters * 2, for the nth beginning of the selector check the data validity in parentheses * 3, match[4] and match[5] respectively stored in xn+b x and b,x and b allowed is negative * 4, return the final match object * * Match[1]: (only|first|last| Nth|nth-last) */match[1] = Match[1].tolowercase ();/* for Nth-child, Nth-of-type, Nth-last-child, Nth-last-of-type four types of brackets domestic demand set valid data * while others are enclosedNo data is allowed in */if (Match[1].slice (0, 3) = = = "Nth") {/* * If there are no valid parameters in the selector brackets, an exception is thrown * Example: if the selector is nth or nth (ABC) is an illegal selector */if (!match[3]) {Sizzle.error (match[0]);} /* * the following nth-child () as an example to explain the syntax, in order to better understand the role of the following code * Nth-child allowed to use the following: *: Nth-child (even) *: Nth-child (ODD) *: Nth-chil D (3n) *: Nth-child (+2n+1) *: Nth-child (2n-1) * In the code below the assignment number to the left of the match[4], match[5] is used to record in parentheses, respectively, before and after n values, including the sign * for: Nth-child (even ) and: Nth-child (Odd), match[4] is empty, * so return 2 * (match[3] = = = "even" | | match[3] = = = "odd") calculation result * because in JS true=1,false=0 , so (match[3] = = = "even" | | match[3] = = = "Odd") equals 1 * Therefore, 2 * (match[3] = = = "even" | | match[3] = = = "Odd") evaluates to 2 * * equals right  The function of the side "+" is to force the type conversion, convert the string after to the numeric type */match[4] = + (Match[4]? Match[5] + (Match[6] | | 1): 2 * (match[3] = = = "even" | | match[3] = = = "Odd")); match[5] = + ((match[7] + match[8]) | | match[3] = = = "Odd");} else if (Match[3]) {/* * If the other child type selector is not nth starts with parentheses, the exception is thrown * Here jquery is not strictly determined by the rules of the, because it allows: this form of first-child () exists * That is, for jquery: First-child () is equivalent to: First-child, which is the legal selector */sizZle.error (Match[0]);}    return match;}, "PSEUDO": function (Match) {/* * * Complete the following tasks: * 1, get the value enclosed in the pseudo-class * 2, for non-quoted values, if there is a pseudo-class nesting, then further resolve to determine the current pseudo-class actual end position, * Gets the full string and value of the current pseudo-class * 3, returning a copy of the first three items in the match. * * unquoted denotes non-quoted values in parentheses, * to: EQ (2) For example, unquoted=2 */var excess, unquoted =!match[5] && match[2];/* * because pseudo and CH The matching regular expression of ILD has a intersection, so the part that belongs to child needs to be ignored */if (matchexpr["Child"].test (Match[0])) {return null;} /* * If the value in parentheses is enclosed in quotation marks (match[3]), * The value of the exception (Match[4]) is assigned to match[2]. * Match[3] denotes quotation marks. */if (Match[3] && match[4]!== undefined) {match[2] = match[4];} else if (unquoted/* * rpseudo.test (unquoted): Used to test unquoted contains pseudo-class, * if it contains pseudo-class, it is possible to have pseudo-class nesting possibility, need to further parse unquoted * For example:: Not (: eq (3)) */&& Rpseudo.test (unquoted) &&/* * Gets the position of the last character in the unquoted (excess = Tokenize (unquoted, True)) &&/* * Unquoted.indexof (")", unquoted.length-excess) * The location of the last character in a successively valid selector that was previously obtained, followed by the position of ")", which is usually after the current position. * Minus Unquoted.length, used to get the valid complete pseudo-class string last position in match[0], * Note that at this point the excess is a negative value */(Excess= Unquoted.indexof (")", unquoted.length-excess)-unquoted.length)) {//Get valid complete pseudo-class match[0] and pseudo-class data in parentheses match[2]match[0] = Match[0].slice (0, excess); match[2] = unquoted.slice (0, excess);} Returns a copy of the first three elements of Match return Match.slice (0, 3);}}

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jquery Selector code detailed (a)--sizzle method

jquery Selector code in detail (ii)--select method

jquery Selector code in detail (iii)--tokenize method

jquery Selector code in detail (iv)--expr.prefilter