What Is JavaScript?

JavaScript is a full-fledged dynamic programming language that, when applied to HTML, can enable interactivity on websites. It enables you to click on buttons, move objects around, and even get real-time updates without the page having to refresh itself. In fact, it’s used to make most of the front end of web pages, including animated images, search bars, image slideshows, chat widgets, and video. It’s also used to create calculators and project management tools that work in-browser, without requiring external software.

JavaScript features a few notable differences from other languages. It uses arrow functions to shorten the syntax, and it also allows you to pass values as function arguments. In addition, it’s a function-oriented language, meaning that most operations are performed on a function object. It uses just-in-time compilation, so simple functions run very quickly and can be executed right in the browser. This is a much faster approach than ahead-of-time compilation, which is commonly used in languages like C and C++.

Variables in javascript can be declared using one of three keywords: let, const, and var. let declarations make the variable available at block-level, while const prevents reassignments, but does not prevent mutations of the value. var declarations are not blocked-scoped, so they can cause side effects if you change their value.

There are two types of values in javascript: strings and numbers. Strings can be enclosed in single or double quotes, while numbers don’t require them. You can also use special symbols like’and’to create unique identifiers that won’t collide.

Functions in javascript can accept any number of argument values and return a result. The function name must be followed by parentheses, and each argument must be separated by commas if it’s more than one. It’s important to note that if the expression inside the parentheses is a comparison (like if the variable iceCream is equal to the string chocolate), it must be done with strict equality, not just any kind of equality. There are many other operators in javascript, including bitwise and logical ones.

Because javascript is a scripting language, it can travel the element family tree, or DOM, of an HTML document and access, modify, or even delete elements in the document. Frequent interaction with the DOM can slow down performance and lead to lag in your web application, so you can use techniques like minimizing DOM manipulation and reducing function calls to increase efficiency and speed. This is a key factor in ensuring your applications are responsive and smooth.