this will do the trick for you
if (!!val) {
alert("this is not null")
} else {
alert("this is null")
}
Mozilla
developer.mozilla.org › en-US › docs › Web › JavaScript › Guide › Data_structures
JavaScript data types and data structures - JavaScript | MDN
All primitive types, except null and undefined, have their corresponding object wrapper types, which provide useful methods for working with the primitive values. For example, the Number object provides methods like toExponential(). When a property is accessed on a primitive value, JavaScript automatically wraps the value into the corresponding wrapper object and accesses the property on the object instead.
Top answer 1 of 10
169
this will do the trick for you
if (!!val) {
alert("this is not null")
} else {
alert("this is null")
}
2 of 10
150
There are 3 ways to check for "not null". My recommendation is to use the Strict Not Version.
1. Strict Not Version
if (val !== null) { ... }
The Strict Not Version uses the Strict Equality Comparison Algorithm. The !== operator has faster performance than the != operator, because the Strict Equality Comparison Algorithm doesn't typecast values.
2. Non-strict Not Version
if (val != null) { ... }
The Non-strict Not Version uses the Abstract Equality Comparison Algorithm. The != operator has slower performance than the !== operator, because the Abstract Equality Comparison Algorithm typecasts values.
3. Double Not Version
if (!!val) { ... }
The Double Not Version has faster performance than both the Strict Not Version and the Non-Strict Not Version. However, the !! operator will typecast "falsey" values like 0, '', undefined and NaN into false, which may lead to unexpected results, and it has worse readability because null isn't explicitly stated.
Good way to check for variable being not null and not undefined.
There are some style guides that basically say you always should use ===, but you can use == in order to check for null or undefined at the same time. So you could do the following: if (value != null) { // This will run if `value` is not `null` and not `undefined`. } More on reddit.com
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32
October 20, 2016Could someone explain why "" != null? - JavaScript - SitePoint Forums | Web Development & Design Community
Where I tried to find out if field is empty and I checked against null, where it failed, then I replaced it with "" (nothing) and it started working as intended… why does null not work? ... I’m not really into javascript, but in php "" is setting the variable to an empty string, with emphasis ... More on sitepoint.com
0
October 14, 2016What’s the best way to use JavaScript if not null to check if a variable is not null? - LambdaTest Community
What’s the best way to use JavaScript if not null to check if a variable is not null · This solution is the most general and checks if myVar is a truthy value. It works for any value that is not falsy, including null, undefined, false, 0, NaN, and "". It’s useful if you want to ensure ... More on community.lambdatest.com
0
April 1, 2025Why is my PHP variable passing as "null" in jQuery AJAX?
uuuuuuh where is the variable "formData" coming from?
and where are you getting nulls? are you saying name and person are null? Have you looked at it in a debugger?
More on reddit.com 14
2
September 18, 2013Videos
05:53
How to Check for Undefined or Null in JavaScript (2025) - YouTube
02:58
How to check null in Javascript using 2 ways tutorial - YouTube
07:53
How to check if a value is not null and not empty string in JS ...
03:09
JavaScript Check null, undefined, empty, NaN & false values - YouTube
Best Way to Check 'Null', 'Undefined' or 'Empty' in JavaScript ...
01:01
undefined is not null in javascript - YouTube
Codedamn
codedamn.com › news › javascript
How to check if value is undefined or null in JavaScript
June 8, 2023 - The easiest way to check if a value is either undefined or null is by using the equality operator (==). The equality operator performs type coercion, which means it converts the operands to the same type before making the comparison.
ServiceNow Community
servicenow.com › community › in-other-news › undefined-null-and-oh-my › ba-p › 2291977
undefined, null, ==, !=, ===, and !== - Oh My! - ServiceNow Community
June 3, 2024 - The undefined value is actually implemented in JavaScript by a special Undefined object, which only has one instance (it's a singleton). Horace has an SSN property, because he's a U.S. citizen, but he forgot what it was — so we assigned a null for him (Horace is a null kinda guy, actually). Note that difference between null and undefined: the former indicates that the property is there, but it doesn't refer to any value at the moment; the latter says the property isn't even there.
Reddit
reddit.com › r/javascript › good way to check for variable being not null and not undefined.
r/javascript on Reddit: Good way to check for variable being not null and not undefined.
October 20, 2016 -
Hi, all, I often do stuff like this in my code, to check for a variable being not null and not undefined.
// check if value is not null and not undefined
if (value) {
...
}However, I'm now thinking this can leads to bugs, because of 0, "", false and NaN also being falsy.
What is a better way to check a variable is not null and not undefined? I could use this I think, wondering if there is something shorter than this:
if (typeof value !== 'undefined' || value !== null) {
...
} Top answer 1 of 5
29
There are some style guides that basically say you always should use ===, but you can use == in order to check for null or undefined at the same time. So you could do the following: if (value != null) { // This will run if `value` is not `null` and not `undefined`. }
2 of 5
18
fyi your if statement doesn't match your description of it: What is a better way to check a variable is not null and not undefined? what you have now checks if it's not null or not undefined, which will always pass the check and enter the body of the if statement. you want something like: if (typeof value !== 'undefined' && value !== null) { ... } But honestly, the majority of the time if (value) { ... } is exactly what you want, and is well understood and idiomatic
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › Nullish_coalescing
Nullish coalescing operator (??) - JavaScript | MDN
const count = 0; const text = ""; const qty = count || 42; const message = text || "hi!"; console.log(qty); // 42 and not 0 console.log(message); // "hi!" and not "" The nullish coalescing operator avoids this pitfall by only returning the second operand when the first one evaluates to either null or undefined (but no other falsy values): ... const myText = ""; // An empty string (which is also a falsy value) const notFalsyText = myText || "Hello world"; console.log(notFalsyText); // Hello world const preservingFalsy = myText ??
Dmitri Pavlutin
dmitripavlutin.com › javascript-null
Everything about null in JavaScript
September 21, 2020 - The good way to check for null is by using the strict equality operator: ... If the variable contains a non-null value, like an object, the expression existingObject === null evaluates to false. null, alongside false, 0, '', undefined, NaN, ...
GeeksforGeeks
geeksforgeeks.org › javascript › how-to-check-if-a-variable-is-not-null-in-javascript
How to check if a Variable Is Not Null in JavaScript ? - GeeksforGeeks
August 5, 2025 - In JavaScript, checking if a variable is not null ensures that the variable has been assigned a value and is not empty or uninitialized.
freeCodeCamp
freecodecamp.org › news › how-to-check-for-null-in-javascript
JS Check for Null – Null Checking in JavaScript Explained
November 7, 2024 - Null is a primitive type in JavaScript. This means you are supposed to be able to check if a variable is null with the typeof() method. But unfortunately, this returns “object” because of an historical bug that cannot be fixed. let userName ...
TypeScript
typescriptlang.org › docs › handbook › 2 › everyday-types.html
TypeScript: Documentation - Everyday Types
JavaScript has two primitive values used to signal absent or uninitialized value: null and undefined. TypeScript has two corresponding types by the same names. How these types behave depends on whether you have the strictNullChecks option on. With strictNullChecks off, values that might be ...
ThatSoftwareDude.com
thatsoftwaredude.com › content › 8774 › what-is-the-best-way-to-check-for-an-empty-string-in-javascript
The Best Way to Check for an Empty String in JavaScript - ThatSoftwareDude.com
August 23, 2024 - Want to check if a string is empty in JavaScript? There are several ways to do it, but not all are equally readable, safe, or performant. In...
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › null
null - JavaScript | MDN
October 28, 2025 - Unlike undefined, JSON.stringify() can represent null faithfully. JavaScript is unique to have two nullish values: null and undefined. Semantically, their difference is very minor: undefined represents the absence of a value, while null represents the absence of an object.
W3Schools
w3schools.com › sql › sql_null_values.asp
SQL NULL Values - IS NULL and IS NOT NULL
SELECT CustomerName, ContactName, ... Address IS NOT NULL; Try it Yourself » ... If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail: [email protected] · If you want to report an error, or if you want to make a suggestion, send us an e-mail: [email protected] · HTML Tutorial CSS Tutorial JavaScript Tutorial How ...
LogRocket
blog.logrocket.com › home › how to check for null, undefined, or empty values in javascript
How to check for null, undefined, or empty values in JavaScript - LogRocket Blog
February 14, 2025 - Checking for null can be nerve-wracking for both new and seasoned JavaScript developers. It’s something that should be very simple, but still bites a surprising amount of people. The basic reason for this is that in most languages, we only have to cater to null.
freeCodeCamp
freecodecamp.org › news › check-if-string-is-empty-or-null-javascript
How to Check if a String is Empty or Null in JavaScript – JS Tutorial
November 7, 2024 - In this example, we're first using the trim method to remove any leading or trailing whitespace characters from the str variable, then checking whether the resulting string has zero length. If it does, then we know that the string is empty. Otherwise, we know that the string is not empty. Here are some best practices to follow when checking for empty or null strings in JavaScript:
Stack Abuse
stackabuse.com › javascript-check-if-variable-is-a-undefined-or-null
JavaScript: Check if Variable is undefined or null
March 29, 2023 - In this short guide, we've taken a look at how to check if a variable is null, undefined or nil in JavaScript, using the ==, === and typeof operators, noting the pros and cons of each approach.
Medium
medium.com › @python-javascript-php-html-css › how-to-check-for-empty-undefined-or-null-strings-in-javascript-d8f0bf514ead
How to Use JavaScript to Check for Null, Empty, or Undefined Strings
August 24, 2024 - In the first script, we create a function called isStringEmpty that accepts a single parameter, value. This function returns true if the value is either undefined, null, or an empty string (“”).
GeeksforGeeks
geeksforgeeks.org › javascript › how-to-check-for-null-values-in-javascript
How to check for null values in JavaScript ? - GeeksforGeeks
July 23, 2025 - That is because a variable that has been declared but not assigned any value is undefined, not null. ... By this operator, we will learn how to check for null values in JavaScript by the (===) operator.
SitePoint
sitepoint.com › javascript
Could someone explain why "" != null? - JavaScript - SitePoint Forums | Web Development & Design Community
October 14, 2016 - Not quite - if you declare a variable without assigning a value, its value will be undefined. ... @fretburner Yes you are correct that is a caveat in javascript i tend to overlook the everything is an object crap. But what i was refering to is how the interpreter most of the time in many languages uses just memory to check the value. Since null is a primitive type object in javascript undefined and null are different in terms of how memory see’s them that is a great point.
LambdaTest Community
community.lambdatest.com › general discussions
What’s the best way to use JavaScript if not null to check if a variable is not null? - LambdaTest Community
April 1, 2025 - What’s the best way to use JavaScript if not null to check if a variable is not null · This solution is the most general and checks if myVar is a truthy value. It works for any value that is not falsy, including null, undefined, false, 0, NaN, and "". It’s useful if you want to ensure ...