详解express使用vue-router的history踩坑

var rewrite = options.rewrites[i];
var match = parsedUrl.pathname.match(rewrite.from);
if (match !== null) {
rewriteTarget = evaluateRewriteRule(parsedUrl, match, rewrite.to, req);

if(rewriteTarget.charAt(0) !== '/') {
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);
req.url = rewriteTarget;
return next();
}
}

var pathname = parsedUrl.pathname;
if (pathname.lastIndexOf('.') > pathname.lastIndexOf('/') &&
options.disableDotRule !== true) {
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 or function.');
}

return rule({
parsedUrl: parsedUrl,
match: match,
request: 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 && options.logger) {
return options.logger;
} else if (options && options.verbose) {
return console.log.bind(console);
}
return function(){};
}

这个代码还真是通俗易懂，就不去一行行分析了（其实是我懒）。直接截取关键代码：

else if (!acceptsHtml(headers.accept, options)) {
   logger(
    'Not rewriting',
    req.method,
    req.url,
    'because the client does not accept HTML.'
   );
   return next();
  }

function acceptsHtml(header, options) {
 //在这里
 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;
}

前一段代码，如果 acceptsHtml 函数返回 false，说明浏览器不接受 html 文件，跳过执行 next()，否则继续执行。