javascript check if not null or undefined

How to check empty/undefined/null string in JavaScript? There's more! Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How to get the first non-null/undefined argument in JavaScript Using Kolmogorov complexity to measure difficulty of problems? This example checks a variable of type string or object checks. In practice, most of the null and undefined values arise from human error during programming, and these two go together in most cases. ), which is useful to access a property of an object which may be null or undefined. Solution is drawn keeping in mind the resuability and flexibility. Very important difference (which was already mentioned in the question btw). I use it as a function parameter and exclude it on function execution that way I get the "real" undefined. Now, we can use the library to check whether a variable is null, undefined or nil - where nil refers to both of the previous two afflictions. }. It's been nearly five years since this post was first made, and JavaScript has come a long way. ; This is a bit contentious, but I would generally advise typeof undefined over "undefined". What is JavaScript Null, Undefined and NaN - AppDividend Of course you could just use typeof though. I created a jsperf entry to compare the correctness and performance of these approaches. Has 90% of ice around Antarctica disappeared in less than a decade? The null with == checks for both null and undefined values. If, @Laurent: A joke right? This is an idiomatic pattern in JavaScript, but it gets verbose when the chain is long, and it's not safe. This method has one drawback. How do I check if an array includes a value in JavaScript? If you truly want to confirm that a variable is not null and not an empty string specifically, you would write: Notice that I changed your code to check for type equality (!==|===). How to Use the JavaScript Fetch API to Get Data? Finally, we've taken a quick look at using Lodash - a popular convenience utility library to perform the same checks. A difference of 3.4 nanoseconds is nothing. However, due to the typo, somevariable is checked instead, and the result is: In a more complex scenario - it might be harder to spot this typo than in this one. 2023 Studytonight Technologies Pvt. Hide elements in HTML using display property.

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