どのようにNodejsにH 5 Historyモードをサポートさせますか?(connect-history-appi-fallbackソース分析)


読み解く
本論文は主にconnect-history-appi-fallbackライブラリのソースコード分析を行います。connect-history-appi-fallbackは、SPA Historyルーティングモードをサポートするためのnodejsライブラリです。本文を読む前に、HTML 5 Historyモードに対応してある程度の理解があります。
ソース分析

/** 
 *       history  ,     url         api       , localhost:4200/home  url,        “     html,      ”,         。
 *           ,                。
 * connect-history-api-fallback                    ,           !
 *                 ,       ,   !
 */

'use strict';

var url = require('url');

exports = module.exports = function historyApiFallback(options) {
 //       
 options = options || {};
 //         
 var logger = getLogger(options);

 //             ,     req, res, next
 return function(req, res, next) {
  var headers = req.headers;
  if (req.method !== 'GET') {
   //         GET  ,       html,     next(),           
   logger(
    'Not rewriting',
    req.method,
    req.url,
    'because the method is not GET.'
   );
   return next();
  } else if (!headers || typeof headers.accept !== 'string') {
   //        ,       accept     ,         http  ,     ,           
   logger(
    'Not rewriting',
    req.method,
    req.url,
    'because the client did not send an HTTP accept header.'
   );
   return next();
  } else if (headers.accept.indexOf('application/json') === 0) {
   //          application/json     ,        html,     ,           
   logger(
    'Not rewriting',
    req.method,
    req.url,
    'because the client prefers JSON.'
   );
   return next();
  } else if (!acceptsHtml(headers.accept, options)) {
   //             Accept     ['text/html', '*/*'],          html,     ,           
   logger(
    'Not rewriting',
    req.method,
    req.url,
    'because the client does not accept HTML.'
   );
   return next();
  }

  //           html ,       

  //     url   parse     url,       ,  protocol,hash,path, pathname, query, search   ,      location  
  var parsedUrl = url.parse(req.url);
  var rewriteTarget;
  //         rewrites,        ;
  //           ,      from to    ;
  // from       pathname        ;
  // to      url,to        ,                  ,             context,context      (parsedUrl,match,request)
  options.rewrites = options.rewrites || [];
  //          
  for (var i = 0; i < options.rewrites.length; i++) {
   var rewrite = options.rewrites[i];
   //       match     
   var match = parsedUrl.pathname.match(rewrite.from);
   if (match !== null) {
    //   match  null,  pathname          
    rewriteTarget = evaluateRewriteRule(parsedUrl, match, rewrite.to, req);

    if(rewriteTarget.charAt(0) !== '/') {
     //     /            url
     logger(
      'We recommend using an absolute path for the rewrite target.',
      'Received a non-absolute rewrite target',
      rewriteTarget,
      'for URL',
      req.url
     );
    }

    logger('Rewriting', req.method, req.url, 'to', rewriteTarget);
    //      url  
    req.url = rewriteTarget;
    return next();
   }
  }

  var pathname = parsedUrl.pathname;
  //       :           url    .  , .         ,   history          
  //           “      ”
  // disableDotRule true,          
  if (pathname.lastIndexOf('.') > pathname.lastIndexOf('/') &&
    options.disableDotRule !== true) {
   //   pathname     /    .,      /a/b/c/d.*   (*        );
   //       disableDotRule false,          ,      ,       
   logger(
    'Not rewriting',
    req.method,
    req.url,
    'because the path includes a dot (.) character.'
   );
   return next();
  }

  //   pathname    /    .,  disableDotRule true,        :  url
  //   url    /index.html,         index   
  rewriteTarget = options.index || '/index.html';
  logger('Rewriting', req.method, req.url, 'to', rewriteTarget);
  //   url
  req.url = rewriteTarget;
  //                (url   index.html ,                ,       html        ,    !)
  next();
 };
};

//          to
function evaluateRewriteRule(parsedUrl, match, rule, req) {
 if (typeof rule === 'string') {
  //       ,    
  return rule;
 } else if (typeof rule !== 'function') {
  //       ,    
  throw new Error('Rewrite rule can only be of type string or function.');
 }

 //           ,        url
 return rule({
  parsedUrl: parsedUrl,
  match: match,
  request: req
 });
}

//       accept                   
function acceptsHtml(header, options) {
 options.htmlAcceptHeaders = options.htmlAcceptHeaders || ['text/html', '*/*'];
 for (var i = 0; i < options.htmlAcceptHeaders.length; i++) {
  if (header.indexOf(options.htmlAcceptHeaders[i]) !== -1) {
   return true;
  }
 }
 return false;
}

//     
function getLogger(options) {
 if (options && options.logger) {
  //           ,          
  return options.logger;
 } else if (options && options.verbose) {
  //   ,     verbose,    console.log      
  return console.log.bind(console);
 }
 //          ,       
 return function(){};
}

以上が本文の全部です。皆さんの勉強に役に立つように、私たちを応援してください。