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, 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.

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

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

Null-checking in JavaScript - DEV Community

April 11, 2019 - I get it—we need to prevent things from going wrong, but the sight of it brings helicopter parenting to mind. Also, it's not really null-checking, but also undefined- and empty-string-checking. This is another benefit you can gain from TypeScript—the peace of mind that it won't compile if you're sending the wrong information.

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

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`.

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 ...

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..

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.

stackoverflow.com › questions › 43309712 › how-to-check-if-a-value-is-not-null-and-not-empty-string-in-js

javascript - How to check if a value is not null and not empty string in JS - Stack Overflow

If you truly want to confirm that a variable is not null and not an empty string specifically, you would write:

if(data !== null && data !== '') {
   // do something
}

Notice that I changed your code to check for type equality (!==|===).

If, however you just want to make sure, that a code will run only for "reasonable" values, then you can, as others have stated already, write:

if (data) {
  // do something
}

Since, in javascript, both null values, and empty strings, equals to false (i.e. null == false).

The difference between those 2 parts of code is that, for the first one, every value that is not specifically null or an empty string, will enter the if. But, on the second one, every true-ish value will enter the if: false, 0, null, undefined and empty strings, would not.

Instead of using

if(data !== null && data !== ''  && data!==undefined) {

// do something
}

You can use below simple code

if(Boolean(value)){ 
// do something 
}

Values that are intuitively “empty”, like 0, an empty string, null, undefined, and NaN, become false
Other values become true

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.

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

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, ...

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.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 - Loose Equality (`==`): For `0 == null`, JavaScript does not perform the same type conversion. Instead, it treats `null` and `undefined` as loosely equal to each other and not to any other types, including numbers. This special handling ensures that `null` is only equal to `undefined` and not to `0`.

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:

ServiceNow Community

servicenow.com › community › developer-forum › which-is-best-method-to-check-null-not-null › m-p › 2626716

Solved: Re: which is best method to check null / not null - ServiceNow Community

Hey Supriya! · Yes you use that. · also try gr.getValue(assigned_to) // getValue returns null when the value is empty string,but it also returns null when the value is bool "false". · Try log statements to check values you are getting. · · Please hit the thumb and Mark as correct based on Impact!! · Kind Regards, · Ravi Chandra.

can we use if( gr.assigned_to == " " ) if( gr.assigned_to != " " ) ?