Add parse() static factory method

README.md

@@ -30,6 +30,10 @@ This package's algorithms conform to those of the WHATWG [MIME Sniffing Standard
 
 This package's main module's default export is a class, `MIMEType`. Its constructor takes a string which it will attempt to parse into a MIME type; if parsing fails, an `Error` will be thrown.
 
+### The `parse()` static factory method
+
+As an alternative to the constructor, you can use `MIMEType.parse(string)`. The only difference is that `parse()` will return `null` on failed parsing, whereas the constructor will throw. It thus makes the most sense to use the constructor in cases where unparseable MIME types would be exceptional, and use `parse()` when dealing with input from some unconstrained source.
+
 ### Properties
 
 - `type`: the MIME type's [type](https://mimesniff.spec.whatwg.org/#mime-type-type), e.g. `"text"`

lib/mime-type.js

@@ -20,6 +20,14 @@ module.exports = class MIMEType {
     this._parameters = new MIMETypeParameters(result.parameters);
   }
 
+  static parse(string) {
+    try {
+      return new this(string);
+    } catch (e) {
+      return null;
+    }
+  }
+
   get essence() {
     return `${this.type}/${this.subtype}`;
   }

test/api.js

@@ -48,6 +48,24 @@ describe("Constructor behavior", () => {
   });
 });
 
+describe("static parse() behavior", () => {
+  it("converts incoming arguments into strings", () => {
+    const arg = {
+      toString() {
+        return "text/HTML";
+      }
+    };
+    const mimeType = MIMEType.parse(arg);
+
+    expect(mimeType.toString()).toEqual("text/html");
+  });
+
+  it("returns null on unparseable MIME types", () => {
+    expect(MIMEType.parse("asdf")).toBe(null);
+    expect(MIMEType.parse("text/html™")).toBe(null);
+  });
+});
+
 describe("type manipulation", () => {
   let mimeType;
   beforeEach(() => {