this will do the trick for you
if (!!val) {
alert("this is not null")
} else {
alert("this is null")
}
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 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 “null is not an object”
Guessing some amount of time and using a setTimeout is a bad strategy, because the amount of time it'll take for the page to get loaded and parsed can vary. If you're correct that the problem is the elements not being parsed at the point you're trying to select them, you need to wrap all your function calls in an event listener for either the DOMContentLoaded event or the load event. These enable you to reliably execute your code only once the page has finished parsing.
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March 10, 2019JavaScript textContent not working?
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November 8, 2022Why does Object.create(null) not generate an instance of an Object?
I find it helpful how TypeScript handles this issue. It has two different static types for plain objects. On one hand, there is the type object for all objects. The lowercase spelling is also used by typeof: > typeof Object.create(null) 'object' > typeof {} 'object' On the other hand, there is the type Object for instances of Object: > Object.create(null) instanceof Object false > ({}) instanceof Object true Why is Object.create(null) not an instance of Object? The following two expressions are equivalent: obj instanceof C C.prototype.isPrototypeOf(obj) And Object.prototype is not in the prototype chain of obj. (Edit: clarified that TypeScript has two different static types.) More on reddit.com
8
3
December 6, 2019Good 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
56
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October 20, 2016Videos
02:58
How to check null in Javascript using 2 ways tutorial - YouTube
05:53
How to Check for Undefined or Null in JavaScript - YouTube
Null and Undefined in JavaScript - JavaScript Course 2026
07:53
How to check if a value is not null and not empty string in JS ...
15:23
null и undefined / Как проверить значение на ...
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.
MDN Web Docs
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.
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 › 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 ...
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:
DEV Community
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.
Stack Abuse
stackabuse.com › javascript-check-if-variable-is-a-undefined-or-null
JavaScript: Check if Variable is undefined or null
March 29, 2023 - On the other hand, a is quite literally nothing. No assignment was done and it's fully unclear what it should or could be. In practice, most of the null and undefined values arise from human error during programming, and these two go together in most cases. When checking for one - we typically check for the other as well. There are two approaches you can opt for when checking whether a variable is undefined or null in vanilla JavaScript...
Drizzle ORM
orm.drizzle.team › docs › sql-schema-declaration
Drizzle ORM - Schema
This parameter will help you specify the database model naming convention and will attempt to map all JavaScript keys accordingly · // schema.ts import { drizzle } from "drizzle-orm/node-postgres"; import { integer, pgTable, varchar } from "drizzle-orm/pg-core"; export const users = pgTable('users', { id: integer(), firstName: varchar() }) // db.ts const db = drizzle({ connection: process.env.DATABASE_URL, casing: 'snake_case' }) ... There are a few tricks you can use with Drizzle ORM. As long as Drizzle is entirely in TypeScript files, you can essentially do anything you would in a simple TypeScript project with your code.
TutorialsPoint
tutorialspoint.com › article › How-to-check-for-null-undefined-or-blank-variables-in-JavaScript
How to check for null, undefined, or blank variables in JavaScript?
August 8, 2022 - if (variable === null || variable === undefined) { // variable is null or undefined }
freeCodeCamp
freecodecamp.org › news › javascript-nullable-how-to-check-for-null-in-js
JavaScript Nullable – How to Check for Null in JS
July 7, 2022 - null === undefined evaluates as false because they are not, in fact, equal. <null_variable> === null is the best way to strictly check for null. Object.is(<null_variable>,null) is an equally reliable way to check for null.
GitHub
gist.github.com › the-vishal-kumar › dad8faf34c103e722ad74484ae8ef0fc
How to check for null in JavaScript · GitHub
Checking for null is a common task ... empty objects are truthy, so typeof maybeNull === "object" && !maybeNull is an easy way to check that a value is not null...
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.
W3Schools
w3schools.com › typescript › typescript_null.php
TypeScript Null & Undefined
Nullish coalescing is another JavaScript feature that also works well with TypeScript's null handling. It allows writing expressions that have a fallback specifically when dealing with null or undefined. This is useful when other falsy values can occur in the expression but are still valid. It can be used with the ?? operator in an expression, similar to using the && operator. function printMileage(mileage: number | null | undefined) { console.log(`Mileage: ${mileage ?? 'Not Available'}`); } printMileage(null); // Prints 'Mileage: Not Available' printMileage(0); // Prints 'Mileage: 0' Try it Yourself »
New York State
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Public Inquiry
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myDSS
mydss.mo.gov › renew
Medicaid Annual Renewals | mydss.mo.gov
When you are due for your annual renewal, FSD will send you a letter in the mail. The Annual Renewal Timeline may help you know when to expect this information. If FSD has enough information to check your eligibility, your letter will say that your coverage is renewed and there is nothing else you need to do.
Codersvibe
codersvibe.com › home › javascript › how to check for null values in javascript?
Solved - Check Null Values in JavaScript with examples
June 14, 2023 - You can check null values in javascript in different ways. I will show you a few methods to check for null values in JavaScript with examples. We will use javascript equality operators, Object.is() function and typeof() operator in Javascript to check for null values.
Mozilla
developer.mozilla.org › en-US › docs › Web › JavaScript
JavaScript | MDN
1 month ago - This means that cases where some proposals for new ECMAScript features have already been implemented in browsers, documentation and examples in MDN articles may use some of those new features. Most of the time, this happens between the stages 3 and 4, and is usually before the spec is officially published. Do not confuse JavaScript with the Java programming language — JavaScript is not "Interpreted Java".
Mozilla
developer.mozilla.org › en-US › docs › Web › JavaScript › Guide › Regular_expressions
Regular expressions - JavaScript | MDN
This chapter describes JavaScript regular expressions. It provides a brief overview of each syntax element. For a detailed explanation of each one's semantics, read the regular expressions reference. You construct a regular expression in one of two ways: Using a regular expression literal, which consists of a pattern enclosed between slashes, as follows: ... Regular expression literals provide compilation of the regular expression when the script is ...