this will do the trick for you
if (!!val) {
alert("this is not null")
} else {
alert("this is null")
}
Top answer 1 of 10
170
this will do the trick for you
if (!!val) {
alert("this is not null")
} else {
alert("this is null")
}
2 of 10
152
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.
JavaScript.info
javascript.info › tutorial › the javascript language › javascript fundamentals
Nullish coalescing operator '??'
The nullish coalescing operator is written as two question marks ??. As it treats null and undefined similarly, we’ll use a special term here, in this article. For brevity, we’ll say that a value is “defined” when it’s neither null ...
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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October 20, 2016javascript - Opposite of nullish coalescing operator - Stack Overflow
Nullish coalescing operator allows assigning a variable if it's not null or undefined, or an expression otherwise. a = b ?? other It is an improvement over previously used || because || will also ... More on stackoverflow.com
[AskJS] Nullish Check in conditional
value == null only matches null and undefined, not any other falsy values. This is the only time you should use == over ===. More on reddit.com
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August 16, 2024Thoughts on the Null Coalescing (??) operator precedence?
When something relatively new comes out, it's common for the first few games in town to foul up the artistry. Wirth is a towering intellect in this field, but he screwed up the precedence tables in Pascal. Experience will highlight mistakes, and then it's eventually time to design a new language. ?? clearly goes after function-call and field-access, but before arithmetic. The field-access counterpart .? should be on the same level as non-null field-access .. More on reddit.com
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April 30, 2024Videos
02:45
One Of The Most Important JavaScript Features - Nullish Coalescing ...
11:09
Nullish Coalescing Operator - Unleash the Power of JavaScript Updates ...
17:06
A deep dive to the Non Null Assertion operator of TypeScript - YouTube
06:00
Master the Optional Chaining Operator in JavaScript|React|Nextjs ...
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › Nullish_coalescing
Nullish coalescing operator (??) - JavaScript - MDN Web Docs
... 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 ...
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › Optional_chaining
Optional chaining (?.) - JavaScript - MDN Web Docs - Mozilla
1 month ago - By using the ?. operator instead of just ., JavaScript knows to implicitly check to be sure obj.first is not null or undefined before attempting to access obj.first.second.
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › Nullish_coalescing_assignment
Nullish coalescing assignment (??=) - JavaScript | MDN
In fact, if x is not nullish, y is not evaluated at all. ... You can use the nullish coalescing assignment operator to apply default values to object properties.
TypeScript
typescriptlang.org › docs › handbook › release-notes › typescript-2-0.html
TypeScript: Documentation - TypeScript 2.0
A new ! post-fix expression operator may be used to assert that its operand is non-null and non-undefined in contexts where the type checker is unable to conclude that fact. Specifically, the operation x! produces a value of the type of x with null and undefined excluded. Similar to type assertions of the forms <T>x and x as T, the ! non-null assertion operator is simply removed in the emitted JavaScript code...
Built In
builtin.com › software-engineering-perspectives › javascript-null-check
How to Check for Null in JavaScript | Built In
The double equality == operator confirms the absence of any value and does not directly check for null. But one way to check for null in JavaScript is to check if a value is loosely equal to null using the double equality == operator:
GeeksforGeeks
geeksforgeeks.org › how-to-check-if-a-variable-is-not-null-in-javascript
How to check if a Variable Is Not Null in JavaScript ? | GeeksforGeeks
May 1, 2025 - One of the most direct and simple ways to check if a variable is not null is to use the strict equality operator !==. This operator checks if the value is strictly not equal to null, ensuring there’s no type coercion.
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 ...
freeCodeCamp
freecodecamp.org › news › javascript-advanced-operators
Advanced JavaScript Operators – Nullish Coalescing, Optional Chaining, and Destructuring Assignment
January 4, 2024 - This is why the optional chaining operator was created. The operator returns either the value of the property, or undefined when the property is null or undefined. To use the operator, just add a question mark in front of the dot . notation:
Chris Pietschmann
pietschsoft.com › post › 2008 › 10 › 14 › javascript-gem-null-coalescing-using-the-or-operator
JavaScript: Null Coalesce using the || Operator | Chris Pietschmann
October 14, 2008 - Since JavaScript returns a boolean value of true when your looking at a variable that is not set to null or undefined, you can use the || (or) operator to do null coalescing. Basically, as long as the first value is not null or undefined it’s ...
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.
Medium
medium.com › nerd-for-tech › javascript-better-way-to-check-for-nullish-values-395d08ffe2b1
JavaScript — Better way to check for Nullish values | by Apoorv Tyagi | Nerd For Tech | Medium
December 4, 2021 - We have seen the nullish coalescing operator is really useful when you only care about the null or undefined value for any variable. The whole point of Nullish Coalescing Operator is to distinguish between nullish (null, undefined) and falsey ...
Scaler
scaler.com › home › topics › javascript program to check for null
JavaScript Program to Check for Null - Scaler Topics
May 4, 2023 - Inside the if condition, we have ... true and the value of !x is also true. ... In this approach, we will use the equality operator '==' to check if the variable contains null or not....
JavaScript Tutorial
javascripttutorial.net › home › an essential guide to javascript null
An Essential Guide to JavaScript null
September 29, 2020 - const rect = null; const square ... it’s assigned to an object. To check if a value is not null, you use the strict inequality operator (!==):...
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
Top answer 1 of 6
24
To my knowledge, there is no such operator and also no proposal to add one. Instead you can rely on the standard way to check for nullish values: b == null
a = b == null ? b : func(b)
2 of 6
9
This will not answer the question since it was already answered by @str, I'm just posting this here because I don't have enough rep to comment on @Dalou's answer and don't want people to trip on that answer.
a = (b ?? false) && other
Is not the opposite of ??, since a will take the value of b if b is a falsy value other than undefined/null, like '' or 0 for example.
The opposite of ?? should set a to the value of other even if b is '' or 0.
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › null
null - JavaScript - MDN Web Docs
When checking for null or undefined, beware of the differences between equality (==) and identity (===) operators, as the former performs type-conversion. ... typeof null; // "object" (not "null" for legacy reasons) typeof undefined; // "undefined" null === undefined; // false null == undefined; // true null === null; // true null == null; // true !null; // true Number.isNaN(1 + null); // false Number.isNaN(1 + undefined); // true
Medium
oopanpan.medium.com › nullish-coalescing-operator-in-javascript-c490260433a4
Nullish Coalescing Operator in JavaScript | by Pan Li | Medium
August 15, 2021 - Let me introduce you the nullish ... that we had with the logical OR operator “||”. ... If operandOne is NOT null or undefined then the result will be operandOne....
Medium
medium.com › @maxwellarmah01 › understanding-javascript-comparisons-why-0-is-null-and-not-null-372d84d65284
Understanding JavaScript Comparisons: Why 0 is null and not null | by Maxwell Armah | Medium
June 10, 2024 - The equality operator (`==`), also known as loose equality, follows a different set of rules for type conversion: 1. Type Conversion for Loose Equality: — When comparing a number to `null`, JavaScript treats `null` as a special case. — `null` only loosely equals `undefined` and no other value. It does not convert `null` to `0` as it does in the case of relational comparisons.