Here, are drawbacks/cons of using JavaScript . 1) XML separates data from HTML . Much of the code can be customized by someone who knows proper HTML … Advantages Client-side scripts offer numerous advantages, including: Allow for more interactivity by immediately responding to users' actions. Advantages of JavaScriptSpeed. Advantages of using JavaScript include ease of syntax, versatility, processing speed and access to extensive JavaScript libraries in the public domain. Is this purely because of the tendency of C/Java/etc developers to use JavaScript 'incorrectly' (mostly in a semantic sense, I guess)? The