Press enter or click to view image in full size Ever stumbled upon JavaScript errors and wondered what undefined and not defined really mean? Discover the key differences between these common ... As JavaScript has evolved from its loose dynamically-typed roots into complex front-end architectures, properly handling undefined values has become more important than ever before. In this comprehensive guide based on my decades of experience, you‘ll learn: What undefined means and how it can crash your code 3 main ways to prevent and handle undefined variables Strict vs loose equality checks when testing for undefined undefined vs. null and undeclared references Checking for "falsy ... In this tutorial, you'll learn about the JavaScript undefined and how to handle it effectively. The meaning of UNDEFINED is not defined. How to use undefined in a sentence.
