Javascript check for null or empty string. These checks are crucial for ensuring that your code .

Javascript check for null or empty string Nov 15, 2012 · This checks for the value of the token being null, undefined, "" (an empty string) and also for the case that the value of the key is 'undefined' (undefined as a string). Oct 29, 2024 · In JavaScript, == null is a loose equality check that matches both null and undefined, while === null would match only null specifically. Jan 9, 2025 · When working with strings in TypeScript, it's essential to handle null and empty string cases correctly. In order to understand, Let's analyze what will be the value return by the Javascript Engine when converting undefined , null and '' (An empty string also). (see this if you don't know what I'm talking about) But as a judgement call, I think we could stand to have a relatively simple check for values that are null or empty, so I'm looking for feedback on this implementation of String. Jul 12, 2025 · Approach 1: Using Brute force The brute force approach in JavaScript involves manually checking if a value is null or undefined using if statements. Jun 20, 2021 · The whole point of Nullish Coalescing Operator is to distinguish between nullish (null, undefined) and falsey but defined values (false, 0, ‘’ etc. I want to try to do string call equivalent to the C# String. Let’s consider form entry. Example: In this example, we check if the value is null or undefined, assigns 'default value' if true, and prints 'default value' to the console. If the condition is true, the value is set to a default value. Just follow the guidelines. Jul 18, 2022 · How to Check if a String is Empty, null, or undefined Depending on your scenario, you might want to consider that the string could be a nullish value (null or undefined). In this comprehensive guide, we‘ll explore the critical topic of how to properly check for empty, null, or undefined strings in JavaScript. Number The result is false if the argument is +0, -0, or NaN; otherwise the result is true. In this guide, we’ll demystify how to check for empty, undefined, and null strings in JavaScript. NET's String. See full list on freecodecamp. Apr 19, 2024 · JavaScript How to Check if a String is Empty or Null in JavaScript – JS Tutorial By bomber bot April 19, 2024 As a JavaScript developer, it‘s crucial to validate user input to ensure your application behaves as expected and provides a smooth user experience. IsNullOrEmpty(string) in javascript. Values like undefined, null, "" (empty string), 0, NaN, and false are considered falsy in JavaScript. Ensure robust input validation in your applications. To find the difference between null and undefined, use the triple equality operator or Object. So if you are in a situation were null and undefined values are not allowed, but zero and empty string (and the other falsy values) are allowed, you need to explicitly check for null and undefined. This comprehensive guide explores multiple methods and best practices to safely check for empty/null strings in JavaScript, understand the differences, and handle them gracefully… Nov 5, 2024 · Checking for empty and null strings is an important skill for any JavaScript developer. Let‘s look at how to check for null and empty variables in JavaScript. js Series Overview Node. Whether you're validating user input, processing data, or implementing string manipulation operations, it's important to have robust techniques to check if a string is empty in javascript. How to Check for an Empty String in JavaScript Topic: JavaScript / jQuery Prev | Next Answer: Use the === Operator You can use the strict equality operator (===) to check whether a string is empty or not. Various methods exist, but the typeof, . Sep 17, 2015 · If your variables are containing some values that are truthy, like a string, and that is considered positive in your condition, then you could simply check using Array. Aug 30, 2024 · Checking for empty strings or null values is a frequent task in JavaScript programming. empty ()) How to check for null and empty string? Apr 13, 2022 · Hi, How to check if list is empty So if pass null or empty string to the list. Checking for an empty, undefined, or null string in JavaScript involves verifying if the string is falsy or has a length of zero. Jun 5, 2024 · A string in JavaScript is considered truthy unless it is empty (‘’), null, or undefined, which are all falsy values. is () method. The string. Jul 20, 2024 · When working with JavaScript, it is common to encounter scenarios where you need to validate whether a string is empty, undefined, or null. This is important because op may NOT want to catch things like tabs, for example. These checks are crucial for ensuring that your code Sep 4, 2023 · The code above shows how JavaScript considers the three values to be different. Mar 6, 2023 · Checking for an empty, undefined, or null string in JavaScript can be done using various methods. Apr 26, 2023 · Learn how to check if a string is empty or contains only whitespace characters in JavaScript. Feb 21, 2013 · This is because values such as zero and empty string are also considered falsy but likely in many instances allowable values. In this tutorial, we’ll cover the different ways to check if a string is empty, undefined, or null in JavaScript and provide code examples to help you understand each method. I am trying to create a regex that will return false if the String pattern contains whitespace or is empty. I might still choose to use filter for code succinctness and readability, but either strategy is defensible. If the string's length is equal to `0`, then it's empty, otherwise, it isn't empty. The getElementById method returns an Element object that you can use to interact with the element. null == false). If anything falsey is a potentially valid input (0, false, empty string), I would do something like this instead: var j = (i === null) ? 10 : i; Which will only replace null, rather than anything that can be evaluated to false. either null or undefined". Learn how to validate empty input fields using JavaScript in this Stack Overflow discussion, including code examples and best practices. Oct 2, 2018 · I am working on Angular project and time to time I used to have check undefined or null over Object or it's properties. Is it possible to do something like that in JavaScript to check for NaN? Dec 20, 2021 · Check if a string, object and array in JavaScript is empty, or undefined. Nov 28, 2009 · @CoffeeAddict empty string is falsy in javascript, so yes, the expression evaluates to true if a is "" or any other falsy value (null, false, undefined, 0, NaN). We can use the strict equality operator ( === ) to check whether a string is empty or not. In other cases you may only ensure the value is not an empty string. g. If it was vise versa, then the empty string would evaluate to true and again it would enter the if statement. Jan 31, 2022 · Level up your programming skills with exercises across 52 languages, and insightful discussion with our dedicated team of welcoming mentors. Oct 25, 2011 · 60 I am aware of it being frowned upon to do something like write C# in JavaScript. ) For || (logical OR) nullish and falsey Feb 24, 2011 · How do I check a variable if it's null or undefined and what is the difference between the null and undefined? What is the difference between == and === (it's hard to search Google for "===" )? Aug 4, 2025 · How to Check for Null in JavaScript Null represents an intentional absence of a value, indicating a variable has been declared but has yet to be assigned a value. Aug 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. Apr 1, 2011 · 3143 This question already has answers here: How do I check for an empty/undefined/null string in JavaScript? (57 answers) Mar 15, 2023 · In JavaScript, "" represents the empty string, and we can use the null keyword to initialize the string with a null value. May 7, 2023 · Null was designed to represent the absence of an object or value, so it was given a special value of all zeros. e) null, undefined and empty quotes. Yes, the regex is simple, but it's still less clear. Solution below considers variable empty if one of the following is true: JS thinks that variable is equal to false, which already covers many things like 0, "", [], and even [""] and [0] Value is null or it's type is 'undefined' It is an Mar 24, 2017 · I have tried with !== null, but it is returning PASS even when the field is returning 0 or empty string. So while yes, "white space" encompasses more than null, spaces or blank my answer is intended to answer op's specific question. But it is Aug 16, 2018 · The JSON response looks like this when it is empty when viewed in the browser console: What is the best way to check if a string contains only whitespace? The string is allowed to contain characters combined with whitespace, but not just whitespace. These values represent different states of “nothingness” and can lead to runtime errors if not properly validated. indexOf(undefined) > -1; // contains undefined value If you want to test only if there are empty slots, you can iterate manually with a for loop and check whether all indices between 0 and the length of the array are present, e. The following two functions return true only for undefined, null, empty/whitespace values and false for everything else, such as numbers, Boolean, objects, expressions, etc. Jan 8, 2024 · Introduction TypeScript adds type safety to JavaScript, offering ways to understand and validate your data. elements () && list. The above code works for both null,undefined and empty string like "". If the element is not found, null is returned. I tried below but it does not work. Undefined is a special value, as is a null. empty ()) How to check for null and empty string? Oct 23, 2022 · Learn how to use the length property to check if a string is empty in JavaScript. isEmpty(), String. However, most languages that consume JSON (like JavaScript) will t Jan 9, 2025 · When working with strings in TypeScript, it's essential to handle null and empty string cases correctly. Checking whether strings are empty or null is a fundamental part of input validation. length on undefined. Syntax: x === y; Example: The following code snippets show some comparison of objects. Sometimes, we need to check if the string is empty, undefined, or null while working with the strings. Please hit the thumb and Mark as correct based on Impact!! Kind Regards, Ravi Chandra. equals() and Apache Commons, with examples. Since, in javascript, both null values, and empty strings, equals to false (i. This method returns true if the string is empty (length () is 0), and false if not. Checking for null or empty values before using them in your code is a good defensive coding practice. Explore two different approaches: using a regular expression and the test() method. prototype. How to check if result is not 'Null', 'Undefined' or 'Empty' in JavaScript while using conditions? Lets discuss 'if not undefined, null or empty condition in Jul 18, 2011 · 374 Is it possible somehow to return 0 instead of NaN when parsing values in JavaScript? In case of the empty string parseInt returns NaN. Jul 23, 2025 · Approach 1: By equality Operator (===) By this operator, we will learn how to check for null values in JavaScript by the (===) operator. match(/^\s*$/) is asking "Does the string foo match the state machine defined by the regex?". undefined is Since TypeScript is strongly-typed, simply using if () {} to check for null and undefined doesn't sound right. If any() returns an empty string, !isMobile. How can I check for null values in JavaScript? I wrote the code below but it didn't work. Easiest way to check for null and empty string on a TypeScript number Asked 9 years, 3 months ago Modified 1 year, 4 months ago Viewed 197k times Nov 23, 2017 · When it comes to comparisons, Javascript has a few quirks that are often difficult to remember. Checking for Undefined or Null Using the Equality Operator (==) The easiest way to check if a value is either undefined or null is by using the equality operator (==). If it is null or empty, then trying to assign default value as '1'. Definition and Usage The isEmpty() method checks whether a string is empty or not. getValue (assigned_to) // getValue returns null when the value is empty string,but it also returns null when the value is bool "false". Find out if a string is undefined, null, or empty. Mar 16, 2021 · TL;DR - If any of those six values (false, undefined, null, empty string, NaN, 0) is the first operand of || , then we’ll get the second operand as the result. Try log statements to check values you are getting. You want to check if it's an empty string instead: Feb 23, 2025 · In JavaScript, handling null, undefined, and empty values is critical for building robust applications. f I am trying to check if the string is null or empty. Apr 19, 2012 · I need to check to see if a var is null or has any empty spaces or for that matter just blank. As many know, (0 == "") is true in JavaScript, but since 0 is a value and not empty or null, you may want to test for it. Look at the default examples on lodash and the extra I added. This made it easy for the language to check if a variable was null since it could simply check if the value was equal to zero. js). Mar 10, 2025 · By consistently checking JavaScript strings correctly for being empty, null, or undefined, developers foster robust, reliable, maintainable JavaScript codebases. length, and . Mar 21, 2017 · First check against null then check if the strings aren't empty and to do it the best way would be to compare the string to an empty string which will avoid getting Exceptions if you use . Feb 4, 2023 · Learn how to check if a JavaScript string is empty. The length Property - mostly used The length property can be used to get the length of the given array if it returns 0 then the length of the array is 0 means the given array is empty else the array have the elements. For example, we are taking the details from the users via an HTML form, and users can add an Aug 17, 2024 · How to Check if a String is Empty or Null in JavaScript – JS Tutorial By Alex Mitchell Last Update on August 17, 2024 Strings in JavaScript can be sneaky… Like a spy with multiple identities, strings can appear populated but actually be deceptively empty. Solved: Hi all, In catalog client script, when value is empty or null, how to deal in if condition? eg: Var val; //or val='' whatever. The code will check if the string value is the string "NULL". It helps avoid errors like trying to access properties of null or undefined variables. any() ? false : true will return false, but you probably want true. Empty` equivalent (like in C# or other languages)? Feb 20, 2025 · We can check for this by doing the following: This depends on the object's “truthiness”. Jun 23, 2023 · Discover easy techniques to check if a string is empty in JavaScript! Breakdown of methods, code snippets, and clear explanations for beginners and pros alike. Aug 19, 2019 · To check null in JavaScript, use triple equals operator (===) or Object. I looked online assuming that there was a simple call to make, but I could not find one. Apr 13, 2022 · Hi, How to check if list is empty So if pass null or empty string to the list. Or they might seem configured correctly but turn out to be null or undefined instead! Mar 1, 2024 · Use the `length` property on the string to check if it is empty. Check if a string has any white spaces Next, we are going to check if string is blank or having some white spaces. Each method has its own advantages and disadvantages, and it is important to choose the one that best fits your needs. Handling edge cases with empty strings protects application integrity and prevents bugs that lead to frustrated users. Find the best approach for your validation needs. Dec 22, 2020 · If you coerce that string to a boolean then it should check all your conditions, which is pretty much checking if user. Example empty values include null, undefined, the empty string, and empty arrays. In this tutorial, we are going to show you the ways of checking whether the JavaScript string is empty, undefined, or null. In case of an input element, the value property of the object contains the string in the value attribute. isUndefined() see example below: this. with in operator. Learn best practices to ensure your code handles string validation effectively. Jul 28, 2023 · Hey Supriya! Yes you use that. Learn how to check if a value in JavaScript is null, undefined, or empty. Oct 8, 2010 · Using JavaScript, how do I NOT detect 0, but otherwise detect null or empty strings? Jan 9, 2025 · Lodash _. Aug 13, 2018 · Learn how to check if a model value is empty or null in JavaScript on Stack Overflow. Objects are considered empty if they have no own enumerable string keyed properties. If we want to check specifically for an empty string over null, We would think checking against "" is our best bet, using the === operator. This would make more sense if you were checking for equality and would then read as follows: I have an object: const obj = { name: "", age: null } How can I check if all attributes is null or "" with lodash ? Is so, return true, if some attributes is not null or "" then false. The below approaches can be used to check if the JSON key is null. Jan 4, 2019 · Is there a JavaScript equivalent to . trim () method allows us to remove the space from the start of the string. You're also not guaranteed for trim to be defined via a regex, a lot of JS engines have it built-in. Normally I use lodash _. This means your code is incorrect for this case. Node. IsNullOrWhitespace so that I can check if a textbox on the client-side has any visible text in it? I'd rather do this on the client-side first tha Mar 23, 2023 · The validation steps could require a string value of a given length for a field. It depends how you want to use it. In this article, we will explore effective methods to check the emptiness of a JSON object in JavaScript. Jul 26, 2010 · This is used for validation with a form using JavaScript. In this article, we'll explore the different methods and best practices for checking if a string is null or empty. How to Check for an Empty String in Javascript To check for an empty string, you need to use the equality === operator and see if I know this is really basic, but I am new to javascript and can't find an answer anywhere. Nov 14, 2023 · Empty – This refers to values that have a length of 0, like an empty string "". Start from the fastest way to perform an isEmpty check. May 30, 2019 · Since an empty string does not equal null, the null check is true which means one of the checks evaluated to true and would enter the if statement. e. “Truthy” values like “words” or numbers greater than zero would return true, whereas empty strings would return false. What is the most elegant way to determine if all attributes in a javascript object are either null or the empty string? It should work for an arbitrary number of attributes. isEmpty () method checks if the value is an empty object, collection, map, or set. Feb 28, 2023 · In this tutorial, we'll take a look at how to check if a String is null, empty or blank in Java, using String. Mar 8, 2012 · I know that in most programming scenarios, the preference is for empty collections to null collections when there are 0 elements. However, most languages that consume JSON (like JavaScript) will t Learn how to validate empty input fields using JavaScript in this Stack Overflow discussion, including code examples and best practices. After moving the space, we can check that if the strings length is zero, the string can be either empty, null, or undefined. this if condition doesn't work, it still enters the if statement If (list && list. For us humans, they look the same. The equality operator performs type coercion, which means it converts the operands to the How check string is null or not in JavaScript? Use the === Operator to Check if the String Is Empty in JavaScript. phone is truthy. Dec 4, 2016 · It will not work for checking whether a non-global variable is null or undefined, nor will it work if your JavaScript is running outside a browser (i. String and Whitespace: Handles both empty and whitespace Apr 14, 2016 · arr. This ensures valid data is always present. This check is important for avoiding errors when accessing or manipulating data, ensuring that the variable holds valid, usable content before proceeding with operations. Explore practical examples and best practices for handling these cases in your code. Does TypeScript have any dedicated function or syntax Mar 28, 2024 · How to Check if a JSON Object is Empty or Not in JavaScript In the realm of JavaScript development, working with JSON objects is a common task. We’ll also answer a common question: Does JavaScript have a `string. js Strings Streams Date & Time Arrays Promises JSON Iterators Classes Oct 8, 2015 · 5 Empty string is also a falsy value. Checking if a string is empty is a common operation – and TypeScript provides multiple approaches to this simple yet Mar 11, 2024 · In this tutorial we will show you the solution of JavaScript check for null or empty string, here we used built-in values in javascript (i. trim () approaches are quick and useful in most cases. The comparison data==="" will only return true if the data type of the value is a string, and it is also empty; otherwise, return false . any() !== null. also try gr. Jul 25, 2025 · Explore various JavaScript methods to accurately detect empty strings, whitespace-only strings, null, undefined, and other falsy values. Jun 23, 2023 · Discover easy techniques to check for an empty string in JavaScript! Breakdown of methods, code snippets, and clear explanations for beginners and pros alike. Example: When checking for null variables in JavaScript, there are several standard approaches. We have to be a little careful about this application. Saying foo. Need one condition, which can check both the requirements at the same time and calls ajax if value is not null or empty. Aug 11, 2010 · A note about performance Looping is likely faster in this case, since you can stop looping as soon as you find an empty string. in Node. Dec 24, 2019 · Hello, I was trying to check if a string is null or empty using javascript or jquery , just like we do in C#. Dec 15, 2022 · The Solution To check that a value is not an empty string, null, or undefined, you can create a custom function that returns true if a value is null, undefined, or an empty string and false for all other falsy values and truthy values: Dec 10, 2024 · Checking whether a string value is empty or null in JavaScript is a fundamental skill every developer needs to master. Unless you want to specifically check for undefined or null. JavaScript validation for empty input field Try to submit the form without entering any text. every() Jul 24, 2024 · They are designed to meticulously check if a variable is null, undefined, or lacks content, such as an empty string, array, or object. You can directly check the same on your developer console. Jul 28, 2019 · I didn’t know it is different between primitive values and object/collection types in JavaScript for empty checking. selectedItem. If you needed to loop over all the elements in the array, however-- perhaps to check if every item is the empty string-- filter would likely be much faster Common Approaches Checking for Falsy Values By using the logical NOT operator (!), you can quickly check if a variable is falsy. Jun 4, 2023 · Introduction Working with strings is a common task in JavaScript development. Explore methods to efficiently handle empty, null, or undefined strings. Jan 19, 2018 · You can test for null and return some dependent expression in a single line with the ternary operator ?:, as already given in other answers : (use === null to check only for null s values, and == null to check for null and undefined) Sep 5, 2023 · Learn how to check for an empty string in JavaScript using simple techniques. How can I check if a string is empty? Aug 23, 2024 · Discover the most efficient methods to check for an empty string in JavaScript. Aug 28, 2024 · In Java 8, you can easily check if a string is null or empty using either a combination of == and isEmpty() or by leveraging the Optional class for a more elegant solution. If we don't assign any value to any variable, it is undefined by default. Quirks So there's one quirk that you must know about in Javascript. isNullOrEmpty. Therefore how can I change this regex to match an email address format, or an empty string? From my limited regex knowledge, I think \b matches an empty string, and | means "Or", so I tried to do the following, but it didn't work: Aug 13, 2019 · I'm trying to make a function that would handle white spaces or empty strings using TypeScript I tried this function: export const isEmpty = function (text: string): string { return text === nul Dec 22, 2020 · If you coerce that string to a boolean then it should check all your conditions, which is pretty much checking if user. Using these methods, you can effectively determine whether a Text field is null, empty, or blank in Apex. some, check your browser support. Jul 19, 2023 · check if a state variable is null, undefined, or empty, use the logical OR (||) operator along with nullish coalescing operator (??) If the string is not undefined or null and if you want to check for empty string in Javascript we can use the length property of the string prototype as shown below. This tutorial walks you through the steps of detecting whether a given string value is empty. I see potential shortcomings in many solutions posted above, so I decided to compile my own. Knowing how to determine whether a JSON object is empty or contains data is crucial for robust data handling. Dec 15, 2020 · Does this answer your question? Is there a standard function to check for null, undefined, or blank variables in JavaScript? Aug 10, 2021 · The above snippet will print "This is empty, i. This operator only passes for null values, not for undefined, false, 0, NaN. Jul 11, 2025 · These are the following ways to check whether the given array is empty or not: 1. I'd just do something like isMobile. This guide explains how to detect these states using various techniques, best practices, and real-world examples. trim() == '' is saying "Is this string, ignoring space, empty?". includes(undefined); // has empty slot OR contains undefined value arr. Click to discover more! Mar 25, 2025 · To check if a Text field is blank (null, empty, or contains only whitespace), you can combine the checks using the isBlank () method. These are some of the most common methods for checking for null and values loosely equal to null in JavaScript. Instead of trying to keep it in my head, here's a little cheatsheet I use to keep things in check. Jan 25, 2009 · Is there a null coalescing operator in Javascript? For example, in C#, I can do this: String someString = null; var whatIWant = someString ?? "Cookies!"; The best approximation I can figure out for Jun 8, 2023 · Now that we understand the difference between undefined and null, let's explore different ways to check for these values in JavaScript. Nov 23, 2024 · Learn how to check if a string is empty in TypeScript with simple methods. For now I. String The result is false if the argument is the empty String (its length is zero); otherwise the result is May 10, 2024 · 196 The value of a field can not be null, it's always a string value. Why "Nullish Coalescing Operator"? The || (OR) operator works well but sometimes we only want the other expression to be evaluated when the first operand is only either null or undefined. org Jul 11, 2025 · Empty strings contain no characters, while null strings have no value assigned. However, this is an optional field. Do you have additional questions or suggestions about managing strings in JavaScript? Drop a comment below or explore more about JavaScript string methods on Mozilla MDN! The abstract operation ToBoolean converts its argument to a value of type Boolean according to Table 11: Undefined false Null false Boolean The result equals the input argument (no conversion). So far I have this [^\\s] I think that will make sure the string does not contain whites Aug 4, 2025 · How to Check for Null in JavaScript Null represents an intentional absence of a value, indicating a variable has been declared but has yet to be assigned a value. If you want to check for an empty string, you need to consider what kind of value you expect to receive. Apr 8, 2016 · 18 This question already has answers here: How do I check for an empty/undefined/null string in JavaScript? (56 answers) Aug 5, 2025 · In JavaScript, the JSON Object can contain null values, which should be identified. Note: it uses Array. In which case val != null will return true for undefined or null but not for other falsey values like 0. 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. By using the fact that the && operator short circuits, and that both null and the empty string are considered "falsey" in a boolean context, we Nov 3, 2012 · This article covers a simple function which detects empty values. . Dec 27, 2023 · Making sure strings are not empty, null, or undefined before using them in your code is essential for avoiding subtle bugs and errors down the line. jsqgs cveezcf tmuhh xay hpapsy mscqjiov smtoci tksyhg dhg axge drto jsxu oedgv fvurpuxee bihirk