How to Read Cookies Efficiently in JavaScript: A Concise and Performant Solution?

Efficient JavaScript Function for Reading Cookies

In JavaScript, accessing cookies is a common task when developing stand-alone scripts. However, existing methods like readCookie() from QuirksMode.org can be cumbersome and bulky.

To address this issue, alternative approaches have been proposed, including the method used by jQuery.cookie. While these methods are more compact, they may not offer optimal performance or reliability.

Optimized and Cross-Browser Compatible Solution:

A highly efficient and accurate solution for reading cookies in JavaScript is provided by the following function:

const getCookieValue = (name) => (
  document.cookie.match('(^|;)\s*' + name + '\s*=\s*([^;]+)')?.pop() || ''
);

This function uses a regular expression to extract the value of a specified cookie from the document.cookie string. It considers optional whitespace before and after the cookie name and the equals sign, as per RFC 2109 specifications.

Performance and Compatibility:

Benchmarks have shown that this regex approach provides superior performance compared to other methods across most browsers. It is also cross-browser compatible and ensures reliability by handling potential whitespace issues.

Conclusion:

The getCookieValue function offers a concise, performant, and reliable solution for reading cookies in JavaScript. Its size is significantly reduced compared to previous methods, making it a valuable asset for reducing bloat in stand-alone scripts.

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