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
    Facebook Open Graph META Tags

    It's no secret that Facebook has become a major traffic driver for all types of websites.  Nowadays even large corporations steer consumers toward their Facebook pages instead of the corporate websites directly.  And of course there are Facebook "Like" and "Recommend" widgets on every website.  One...

  • By
    CSS 3D Folding Animation

    Google Plus provides loads of inspiration for front-end developers, especially when it comes to the CSS and JavaScript wonders they create. Last year I duplicated their incredible PhotoStack effect with both MooTools and pure CSS; this time I'm going to duplicate...

Incredible Demos

  • By
    Highlight Table Rows, Columns, and Cells Using MooTools 1.2.3

    Row highlighting and individual cell highlighting in tables is pretty simple in every browser that supports :hover on all elements (basically everything except IE6). Column highlighting is a bit more difficult. Luckily MooTools 1.2.3 makes the process easy. The XHTML A normal table. The cells...

  • By
    Basic AJAX Requests Using MooTools 1.2

    AJAX has become a huge part of the modern web and that wont change in the foreseeable future. MooTools has made AJAX so simple that a rookie developer can get their dynamic pages working in no time. Step 1: The XHTML Here we define two links...

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!