Parse Content-Type Header Strings

This package will parse the Content-Type header field into an introspectable data structure, whose parameters can be manipulated:

const contentTypeParser = require("content-type-parser");
 
const contentType = contentTypeParser(`Text/HTML;Charset="utf-8"`);
 
console.assert(contentType.toString() === "text/html;charset=utf-8");
 
console.assert(contentType.type === "text");
console.assert(contentType.subtype === "html");
console.assert(contentType.get("charset") === "utf-8");
 
contentType.set("charset", "windows-1252");
console.assert(contentType.get("charset") === "windows-1252");
console.assert(contentType.toString() === "text/html;charset=windows-1252");
 
console.assert(contentType.isHTML() === true);
console.assert(contentType.isXML() === false);
console.assert(contentType.isText() === true);

Note how parsing will lowercase the type, subtype, and parameter name tokens (but not parameter values).

If the passed string cannot be parsed as a content-type, contentTypeParser will return null.

ContentType instance API

This package's main module's default export will return an instance of the ContentType class, which has the following public APIs:

Properties

• type: the top-level media type, e.g. "text"
• subtype: the subtype, e.g. "html"
• parameterList: an array of { separator, key, value } pairs representing the parameters. The separator field contains any whitespace, not just the ; character.

Parameter manipulation

In general you should not directly manipulate parameterList. Instead, use the following APIs:

• get("key"): returns the value of the parameter with the given key, or undefined if no such parameter is present
• set("key", "value"): adds the given key/value pair to the parameter list, or overwrites the existing value if an entry already existed

Both of these will lowercase the keys.

MIME type tests

• isHTML(): returns true if this instance's MIME type is the HTML MIME type, "text/html"
• isXML(): returns true if this instance's MIME type is an XML MIME type
• isText(): returns true if this instance's top-level media type is "text"

Serialization

• toString() will return a canonicalized representation of the content-type, re-built from the parsed components

Credits

This package was originally based on the excellent work of @nicolashenry, in jsdom. It has since been pulled out into this separate package.