Understanding Popularity of JavaScript

Why is JavaScript popular in web development?

JavaScript is a powerful, complicated, and often misunderstood computer language. It enables the rapid development of applications in which users can enter data and view results easily.
JavaScript is a scripting language that works well across all platforms and browsers and thereby is popular among developers. Javscript is the defacto client side language of browsers.
JavaScript is an object oriented language that is easier to learn and adapt than other programming languages.
JavaScript has a huge online community that you can get help and assistnace with

The primary advantage to JavaScript, which is also known as ECMAScript, centers around the Web browser, thus having the ability to produce the same results on all platforms supported by the browser. In essence, JavaScript provides cross-browser support.
JavaScript language is executed on the client side rather than server side and as a result, it is a faster and more responsive language that increase performance and reduces network latency. Via JavaScript, all HTML rendering happens in the browser, keeping communication with the server fast and to a minimum.
Third part add-ons are available to extend functionality to web pages and enhance user experience

Security Issues. Javascript snippets, once appended onto web pages execute on client servers immediately and therefore can also be used to exploit the user's system. While a certain restriction is set by modern web standards on browsers, malicious code can still be executed complying with the restrictions set.
JavaScript rendering varies. JavaScript is sometimes interpreted differently by different browsers.