Lets see advantages and disadvantages of JavaScript.
Advantages
JavaScript is supported by most of the web browsers and truly cross platform.
JavaScript is executed on the client side (browser), this means that the JavaScript code is executed on the user’s computer processor/memory space instead of the web server. This saves bandwidth and load on the web server.
JavaScript is a relatively easy language. The JavaScript is very easy to learn. The syntax is easy to understand.
JavaScript is fast to the end user, hence provides seamless user experience
Many modern websites now a days uses JavaScript AJAX methods to fetch data from web servers and render inside web pages at runtime. REST api used for this purpose and the data fetched is in JSON format.
Disadvantages
Security Issues, JavaScript is explicitly added to web pages and client browsers, it can exploit user’s system
Malicious code can be executed on client machine
JavaScript can be disabled from browser, leaving your web page not rendered properly
Buggy JavaScript can crash or take longer time to run and hence increases browser memory and browser might stop responding
Even Though JavaScript is supposed to be cross platform, some features are browser dependent. There are many properties/methods in JavaScript which are implemented differently across browsers.
Most of the JavaScript depends on the manipulation of Browsers DOM elements. And, different browsers given different type of access to objects, specifically Internet Explorer.