When writing JavaScript code, it is important to know the correct way to check if an object property is undefined. The most reliable method to accomplish this is by using the typeof operator. Let me guide you through the process with this easy explanation. To check if an object property is undefined, you simply utilize the typeof operator. This operator returns a string that represents the type of the given operand....
In older code, you may come across a situation where undefined is intentionally passed to a function. Why was this done? I stumbled upon this interesting technique while watching the well-known Paul Irish video about the jQuery source code. This video is from a different era, being 9 years old at the time of writing, and the jQuery source code has since changed, so you won’t find this trick in there anymore....
JavaScript is often said to be untyped, but that’s not entirely accurate. While it is true that JavaScript allows you to assign different types of values to variables, it does have types. In fact, JavaScript provides both primitive types and object types. Let’s take a closer look at the different types in JavaScript: Primitive types JavaScript has several primitive types: Number: All numbers in JavaScript are internally represented as floats. String: A sequence of characters enclosed in quotes....
In JavaScript, both null and undefined are primitive types with different meanings. It is crucial to understand the distinctions between them. undefined: When a variable is declared but not assigned any value, it is considered undefined. For example: let age; // age is undefined It is important to note that attempting to access a variable that has not been declared will result in a ReferenceError: <variable> is not defined error, which is different from undefined....