URL.canParse

By  on  

Parsing of URLs on the client side has been a common practice for two decades. The early days included using illegible regular expressions but the JavaScript specification eventually evolved into a new URL method of parsing URLs. While URL is incredibly useful when a valid URL is provided, an invalid string will throw an error -- yikes! A new method, URL.canParse, will soon be available to validate URLs!

Providing a malformed URL to new URL will throw an error, so every use of new URL would need to be within a try/catch block:

// The correct, safest way
try {
  const url = new URL('https://davidwalsh.name/pornhub-interview');
} catch (e) {
  console.log("Bad URL provided!");
}

// Oops, these are problematic (mostly relative URLs)
new URL('/');
new URL('../');
new URL('/pornhub-interview');
new URL('?q=search+term');
new URL('davidwalsh.name');

// Also works
new URL('javascript:;');

As you can see, strings that would work properly with an <a> tag sometimes won't with new URL. With URL.canParse, you can avoid the try/catch mess to determine URL validity:

// Detect problematic URLs
URL.canParse('/'); // false
URL.canParse('/pornhub-interview'); // false
URL.canParse('davidwalsh.name'); //false

// Proper usage
if (URL.canParse('https://davidwalsh.name/pornhub-interview')) {
  const parsed = new URL('https://davidwalsh.name/pornhub-interview');
}

We've come a long way from cryptic regexes and burner <a> elements to this URL and URL.canParse APIs. URLs represent so much more than location these days, so having a reliable API has helped web developers so much!

Recent Features

  • By
    Create a CSS Flipping Animation

    CSS animations are a lot of fun; the beauty of them is that through many simple properties, you can create anything from an elegant fade in to a WTF-Pixar-would-be-proud effect. One CSS effect somewhere in between is the CSS flip effect, whereby there's...

  • By
    Responsive Images: The Ultimate Guide

    Chances are that any Web designers using our Ghostlab browser testing app, which allows seamless testing across all devices simultaneously, will have worked with responsive design in some shape or form. And as today's websites and devices become ever more varied, a plethora of responsive images...

Incredible Demos

Discussion

  1. picker

    It doesn’t work in Typescript (with node v22 and @types/node v22) because:
    TS2339: Property ‘canParse’ does not exist on type ‘{ new (url: string | URL, base?: string | URL | undefined): URL; prototype: URL; createObjectURL(obj: Blob | MediaSource):
    string; revokeObjectURL(url: string): void; }’.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!