The jquery selector source code interpretation (ii): Select Method _jquery

The/* Select method is one of the core methods of the Sizzle selector package. It mainly completes the following tasks: * 1, call the Tokenize method to complete the resolution of the selector * 2, for no initial collection (that is, seed is not assigned) and is a single block selector (that is, the selector string does not have commas), *
 Complete the following: * 1 for the first selector is the ID type and the context is document, the direct fetch object overrides the incoming context object * 2) If the selector is a single selector and is an ID, class, tag type, fetch and return the matching DOM element directly  * 3) Get the last ID, class, Tag type selector matching DOM element assignment to the initial collection (i.e. seed variable) * 3, get "precompiled" code by calling the compile method and execute, get and return the matching DOM element * * @param selector Has gone to the tail blank selector String * @param the context to perform the matching initial contexts (that is, the DOM element collection).
 If the context is not assigned a value, the document is taken. * @param results has been matched with a partial final result.
 An empty array is assigned if the results is not assigned a value. * @param seed Initial set/function Select (Selector, context, results, seed) {var I, tokens, token, type, find,//Call Tok

	enize function parsing Selector match = tokenize (selector); If you do not provide an initial set if (!seed) {//Try to minimize operations if there be only one group///If there are only a set of selectors, that is, the selector string has no comma if (MATC H.length = = 1) {//Take a shortcut and set the context if the ' root selector/IS ' an ID/* * The following code is used to process the root selector is Shortcut for ID type * * use slice[0 here to create a new set, * Make sure that the original collection will not be changed by the following code/tokens = Match[0] = match[0].slice (0);  * * If the selector starts with the ID type, and the second is a relationship character (that is, a +~> or a space), * Gets the ID's object as the context continues to complete the subsequent match * * Here's The Conditional judgment: * tokens.length > 2: If tokens has more than two selectors * (token = tokens[0]). Type = = "id": the type of the first selector is ID (that is, start with #), * Support.getbyid: Support Geteleme Ntbyid function * Context.nodetype = = = 9:context object is document * documentishtml: Current processing is HTML code * EXPR.RELATIVE[TOKENS[1] . Type]: The second tokens element is a relationship (that is, a +~> or a space) * If all of the above conditions are met, the statement body within the IF (Tokens.length > 2 && (token = Tokens[0]). Type = = "ID" && support.getbyid && context.nodetype = 9 && documentishtml && Expr.relative[tokens[1].type]) {//To point the current context to the Node object context = (expr.find["id") specified by the first ID selector (token.matches[0 ].replace (RuneScape, Funescape), context) | |
				
				[]) [0];
				If no ID object is specified within the current context, the results if (!context) {return results is returned directly; }//Selector string remove the first id selector selector = selector.slice (Tokens.shift (). Value.lengTH); //Fetch A seed set for right-to-left matching/* The function of the while loop below is to get the initial set based on the last ID, class, Tag type selector * To give a simple Example: If the selector is "div[title= ' 2", the * code obtains all the div nodes under the context according to the DIV and assigns the set to the seed variable, * then calls the compile function, produces the precompiled code, * The precompiled code completes in the above Perform a match of [title= ' 2 '] in the initial collection * First, check the selector string for characters that match the needscontext regular expression * If not, then filter the DOM node from right to left according to selector * Otherwise, you will be the precompiled generation 
			 After code execution (calling the Compile method). * * * * "Needscontext": New RegExp ("^" + whitespace * + "*[>+~]|:( Even|odd|eq|gt|lt|nth|first|last) (?: \ \ ("* + whitespace +" * (?:-\ \d) \\d*) "+ whitespace * +" *\\) |) (? =[^-]|$) "," I ") * Needscontext is used to match the following in the selector string: * 1, >+~ three relationship characters * 2,: Even,: Odd, EQ,: GT,: LT,: Nth,: First,: l AST eight pseudo classes * which, (? =[^-]|$) are used to filter out similar to: First-child and other selectors with the above eight words to begin with, * * i = matchexpr["Needscontext"].test (selector ) ?
			0:tokens.length;

				while (i--) {token = tokens[i]; Abort if we hit a combinator//encounters a relationship break out of the loop if (expr.relative[(type = Token.typE)] {break;
					 } if (find = Expr.find[type]) {//Search, expanding context for leading sibling//combinators/* * rsibling = new RegExp (whitespace + "*[+~]") * rsibling is used to determine whether the token selector is a sibling/if (seed = Find (toke N.matches[0].replace (RuneScape, Funescape), rsibling. Test (tokens[0].type) && context.parent Node | | Context))} {//If seed is empty or no tokens remain, we can//return early//remove the newly used selector tokens.
						Splice (i, 1);
						selector = seed.length && toselector (tokens);
							* * If the selector is empty, stating that the selector is only a single ID, class, tag type, * So directly return the results obtained, otherwise, in the acquisition of seed on the basis of continuing to match * */if (!selector) {
							Push.apply (results, seed);
						return results;
					} break; }}}//Compile and execute a filtering function//provide ' match ' to avoid retokenization if we modifi Ed the//selector above * * First executes compile (selector, match), which returns a "precompiled"function, * and then call the function to obtain the final matching result/compile (selector, match) (seed, context,!documentishtml, results, rsibling.test (selector)
	);
return results; }