How to Validate a URL String in JavaScript Without Regular Expressions?

Determining the Validity of a URL String in JavaScript

In the realm of JavaScript, the ability to verify whether a given string qualifies as a URL is a crucial skill. Excluding the use of regular expressions, this task can be effectively achieved.

To ascertain if a string represents a valid HTTP URL, the URL constructor offers a reliable solution. This method triggers an error upon encountering an improperly formatted string. Here's a JavaScript function that leverages this approach:

function isValidHttpUrl(string) {
  let url;

  try {
    url = new URL(string);
  } catch (_) {
    return false;
  }

  return url.protocol === "http:" || url.protocol === "https:";
}

Note: As defined by RFC 3886, a legitimate URL must commence with a scheme (not restricted to HTTP/HTTPS). Consider the following examples:

• www.example.com: Invalid URL (lacks a scheme)
• javascript:void(0): Valid URL, but not an HTTP URL
• http://..: Valid URL with an unusual host (DNS resolution determines accessibility)
• https://example..com: Valid URL, similar to the previous example

The above is the detailed content of How to Validate a URL String in JavaScript Without Regular Expressions?. For more information, please follow other related articles on the PHP Chinese website!