根据特定字符获取整个字符串或子字符串 [英] Get an entire string or a substring, depending on a specific character

问题描述

我有一个包含 MIME 类型的字符串，比如 application/json.现在我想将其与实际的 HTTP 标头进行比较，在本例中为 content-type.

I have a string that contains a MIME type, say application/json. Now I want to compare this against an actual HTTP header, in this case content-type.

如果标头包含 MIME 类型，则很简单:

If the header contains the MIME type, then it's as easy as:

if (mimeType === contentType) { ... }

不幸的是，标题可能包含附加参数.它们总是出现在我感兴趣的值之后，并且它们之间用 ; 分隔.例如，它可以是 application/json;charset=UTF-8.

Unfortunately, the header may contain additional parameters. They always come after the value I'm interested in, and they are separated from it by a ;. E.g., it could be application/json; charset=UTF-8.

所以现在基本上我需要运行:

So now basically I need to run:

if (mimeType === contentType.substring(0, contentType.indexOf(';'))) { ... }

问题是第一种情况仍然可能发生，所以现在我们有:

The problem is that the first case still can happen, so now we have:

if (mimeType === contentType ||
    mimeType === contentType.substring(0, contentType.indexOf(';'))) { ... }

事情开始变得冗长......

Things start to get lengthy…

我可以考虑使用

if (mimeType === contentType.substring(0, mimeType.length)) { ...}

但这也将成功匹配值 application/jsonformatter(这是不需要的).

but this would also successfully match the value application/jsonformatter (which is not desired).

所以，长话短说:有没有比我上面描述的冗长的 if 更好的方法来比较这些值，例如使用正则表达式?

So, to cut a long story short: Is there a better way to compare these values than my lengthy if described above, e.g. using a regular expression?

基本上，我正在考虑根据以下规则在必要时缩短标题的表达式:

Basically I'm thinking of an expression that shortens the header if necessary according to the following rules:

• 如果它包含分号，则返回它之前的部分.
• 如果它不包含分号，则返回所有内容.

最有效的写法是什么?

推荐答案

我建议使用标准的解析模块，例如 media-typer，Express 在其中间件中使用该模块.

I'd recommend using a standard parsing module like media-typer, which Express uses in its middleware.

var typer = require('media-typer');

var obj = typer.parse(contentType);
if (obj.type === 'application' && obj.subtype === 'json'){
    // Success
}

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