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GET parameters are commonly used in web development to pass data through the URL. They play an essential role in tasks such as filtering search results, tracking user actions, or sharing specific views of a web application. Getting and manipulating these parameters in JavaScript is a frequent need for developers working on interactive front-end applications.

When building web applications, you often need to retrieve data encoded in the query string (the portion of the URL after the ? character). For example, consider the following URL:

In this case, the query string contains two parameters: category=electronics and sort=price. You may want to extract these values in your JavaScript code to display relevant content or perform certain actions like API calls or UI updates.

• Parsing the query string correctly to handle potential encoding, such as special characters or spaces.
• Accessing individual parameters in a reliable way.
• Working with cases where certain parameters are optional or undefined.

There are multiple ways to extract GET parameter values from the query string in JavaScript. Below are two common approaches.

Using URLSearchParams

The URLSearchParams interface simplifies the process of working with query strings. It allows you to retrieve GET parameters in a structured and easy-to-use manner.

• The URLSearchParams constructor takes a query string and provides helper methods like .get() to access specific parameters by name.

Optional Features:

• Check if a parameter exists: params.has('key')
• Iterate over all key-value pairs:

• Ensure browser compatibility if supporting outdated browsers. URLSearchParams is widely supported in modern browsers but may not work in older versions of Internet Explorer.

Manual Parsing with String Methods

For older browser support or highly customised behaviour, you can manually parse the query string using JavaScript's string methods like split() and decodeURIComponent().

• Use window.location.search to retrieve the query string.
• Remove the leading ? and split the string into key-value pairs.
• Map the pairs into an object for easy lookup.

• This approach requires more manual effort and is error-prone if the query string format is inconsistent.
• Performance may be slightly worse for lengthy query strings compared to URLSearchParams.

Further Considerations

1. Handling Edge Cases:

   • Always account for parameters that may be missing or empty. For example, params.get('key') returns null if the parameter doesn’t exist.
   • Use decodeURIComponent to handle special characters (e.g., spaces encoded as %20).

2. Security Implications:

   • Be cautious when using input from the query string as it may be manipulated by users.
   • Avoid directly embedding parameters into your UI or making database queries without sanitisation.

3. Performance:

   • For most modern applications, URLSearchParams is the recommended method as it is efficient and built into the language.
   • Manual parsing can still be useful in environments with limited modern browser support.

4. Alternative Scenarios:

   • For back-end environments like Node.js, libraries such as querystring or qs are more suitable for robust query parsing.

Related Resources

• MDN Web Docs: URLSearchParams
• MDN Web Docs: window.location
• Node.js querystring Module Docs