javascript check for not null

stackoverflow.com › questions › 2422946 › javascript-check-for-not-null

this will do the trick for you

if (!!val) {
    alert("this is not null")
} else {
    alert("this is null")
}

stackoverflow.com › questions › 2422946 › javascript-check-for-not-null

javascript check for not null - Stack Overflow

this will do the trick for you

if (!!val) {
    alert("this is not null")
} else {
    alert("this is null")
}

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.

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.

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People also ask

Is null false in JavaScript?

Null is not considered false in JavaScript, but it is considered falsy. This means that null is treated as if it’s false when viewed through boolean logic. However, this is not the same thing as saying null is false or untrue.

builtin.com › software-engineering-perspectives › javascript-null-check

How to Check for Null in JavaScript | Built In

What is a strict null check?

StrictNullChecks is a feature that treats null and undefined as two separate types, reducing errors and making it easier to find coding bugs. It also has stronger measures for defining variables as null or undefined, ensuring variables are declared as null only when it’s safe to do so.

builtin.com › software-engineering-perspectives › javascript-null-check

How to Check for Null in JavaScript | Built In

What is a null check?

In JavaScript, null represents an intentional absence of a value, indicating that a variable has been declared with a null value on purpose. On the other hand, undefined represents the absence of any object value that is unintentional. A null check determines whether a variable has a null value, meaning a valid instance of a type exists.

builtin.com › software-engineering-perspectives › javascript-null-check

How to Check for Null in JavaScript | Built In

developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Operators › null

null - JavaScript | MDN

Unlike undefined, which is a global variable, null is not an identifier but a syntax keyword. ... Like undefined, accessing any property on null throws a TypeError instead of returning undefined or searching prototype chains. Like undefined, null is treated as falsy for boolean operations, ...

dev.to › wolfhoundjesse › null-checking-in-javascript-lc4

Null-checking in JavaScript - DEV Community

April 11, 2019 - As others have said, if (value) will already check for empties and nulls and stuff. However, people (aka me) tend to forget or get confused about how truthy and falsy work in Javascript, or sometimes I need to check that a variable is not null or undefined, but 0 is an acceptable value.

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:

Published August 4, 2025

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) {
  ...
}

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`. }

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

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 ??

Find elsewhere

Google Bing Mojeek

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.

web.dev › learn › javascript › data-types › null-undefined

null and undefined | web.dev

The strict equality operator considers operands of different data types to be unequal. null == undefined > true null === undefined > false · Unlike the reserved keyword null, undefined is a property of the global object.

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 ...

Dmitri Pavlutin

dmitripavlutin.com › javascript-null

Everything about null in JavaScript

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, ...

bobbyhadz.com › blog › javascript-check-if-variable-is-not-null

Check if a Variable is Not NULL in JavaScript | bobbyhadz

Use the strict inequality (!==) operator to check if a variable is not null, e.g. `myVar !== null`.

code.luasoftware.com › tutorials › javascript › javascript-check-if-not-null-and-not-empty-string

Javascript Check if Not Null and Not Empty String

The following is not perfect, but work for most common circumstances. ... You can use lodash isEmpty. _.isEmpty(null); // true_.isEmpty(''); // true_.isEmpty('hello') // false_.isEmpty([]) // true_.isEmpty([1]) // false_.isEmpty({}) // true_.isEmpty({test: true}) // false

stackoverflow.com › questions › 4361585 › how-to-check-if-a-variable-is-not-null

javascript - How to check if a variable is not null? - Stack Overflow

They are not equivalent. The first will execute the block following the if statement if myVar is truthy (i.e. evaluates to true in a conditional), while the second will execute the block if myVar is any value other than null.

The only values that are not truthy in JavaScript are the following (a.k.a. falsy values):

null
undefined
0
"" (the empty string)
false
NaN

Here is how you can test if a variable is not NULL:

if (myVar !== null) {...}

the block will be executed if myVar is not null.. it will be executed if myVar is undefined or false or 0 or NaN or anything else..

javatpoint.com › how-to-check-if-a-variable-is-not-null-in-javascript

How to check if a variable is not NULL in JavaScript - javatpoint

How to check if a variable is not NULL in JavaScript with javascript tutorial, introduction, javascript oops, application of javascript, loop, variable, objects, map, typedarray etc.

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.

tutorialspoint.com › how-do-i-check-for-null-values-in-javascript

How do I check for null values in JavaScript?

The typeof operator may be used to determine the data type of a JavaScript variable. Here we use the typeof operator with the null operator. The (!variable) means the value is not null and if it is checked with the typeof operator variable which has the data type of an object then the value is null.

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.

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:

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.