connect-history-api-fallback 开源项目教程

1. 项目的目录结构及介绍

connect-history-api-fallback 是一个用于处理单页应用（SPA）中路由历史的中间件。以下是其基本的目录结构：

connect-history-api-fallback/
├── LICENSE
├── README.md
├── index.js
├── package.json
└── test/
    ├── index.js
    └── mocha.opts

• LICENSE: 项目的许可证文件。
• README.md: 项目的说明文档。
• index.js: 项目的主文件，包含了中间件的实现。
• package.json: 项目的依赖和配置文件。
• test/: 包含项目的测试文件。
  • index.js: 测试文件。
  • mocha.opts: Mocha 测试框架的配置文件。

2. 项目的启动文件介绍

项目的启动文件是 index.js，它定义了 connect-history-api-fallback 中间件的主要功能。以下是 index.js 的主要内容：

var url = require('url');

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

  return function(req, res, next) {
    var headers = req.headers;
    if (req.method !== 'GET') {
      logger(
        'Not rewriting',
        req.method,
        req.url,
        'because the method is not GET.'
      );
      return next();
    }
    if (!headers || typeof headers.accept !== 'string') {
      return next();
    }
    if (headers.accept.indexOf('application/json') === 0) {
      logger(
        'Not rewriting',
        req.method,
        req.url,
        'because the client prefers JSON.'
      );
      return next();
    }
    if (!acceptsHtml(headers.accept, options)) {
      logger(
        'Not rewriting',
        req.method,
        req.url,
        'because the client does not accept HTML.'
      );
      return next();
    }

    var parsedUrl = url.parse(req.url);
    var rewriteTarget;
    options.rewrites = options.rewrites || [];
    for (var i = 0; i < options.rewrites.length; i++) {
      var rewrite = options.rewrites[i];
      var match = parsedUrl.pathname.match(rewrite.from);
      if (match !== null) {
        rewriteTarget = evaluateRewriteRule(parsedUrl, match, rewrite.to, req);
        logger('Rewriting', req.method, req.url, 'to', rewriteTarget);
        req.url = rewriteTarget;
        return next();
      }
    }

    if (parsedUrl.pathname.indexOf('.') !== -1) {
      logger(
        'Not rewriting',
        req.method,
        req.url,
        'because the path includes a dot (.) character.'
      );
      return next();
    }

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

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 of function.');
  }
  return rule({
    parsedUrl: parsedUrl,
    match: match,
    req: req
  });
}

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.logger) {
    return options.logger;
  } else if (options.verbose) {
    return console