Cannot read property of undefined javascript object log 'd the object. . To fix this error, you need to check on the variable from which you called the replace() method. keys(config)), or even console. This error occurs when you try to read or access a property on an object that is undefined. When pushing an array's contents to another array I get "Uncaught TypeError: Cannot read property 'push' of undefined" error in this snippet. Nov 1, 2015 · Uncaught TypeError: Cannot read property 'canvas' of undefined - Javascript Object Asked 9 years, 11 months ago Modified 9 years, 11 months ago Viewed 4k times Jul 13, 2025 · Since undefined is not an object type, calling a function or a property on such a variable causes the TypeError: Cannot read property 'length' of undefined. Mar 24, 2013 · javascript cannot read property 'width' of undefined Asked 12 years, 7 months ago Modified 12 years, 7 months ago Viewed 5k times Sep 7, 2021 · typeerror: cannot read property of undefined javascript - empty JSON object from fetch despite postman showing object from API Asked 3 years, 4 months ago Modified 3 years, 4 months ago Viewed 195 times Jul 6, 2023 · The`TypeError: Cannot read property ‘length’ of null` error happens when trying to access the length property of an object that should be an array or string, but is actually null or undefined. Mar 10, 2015 · However, when I create another function to manipulate the objects in the "Formula" array I get an "Uncaught TypeError: Cannot define property 'carrier' of undefined" using this function: Dec 9, 2021 · With TypeScript, there are two ways of interpreting null and undefined types and one of them can avoid the 'Cannot read properties of undefined' runtime TypeError. log(Object. 5K subscribers Subscribe Dec 6, 2024 · The error Cannot read property 'forEach' of undefined in JavaScript typically occurs when you attempt to call the forEach method on a variable that is either undefined or not an array. therefore you won't see the log you'd see otherwise. g. In this article, we will learn how to solve this error effectively and prevent it from happening in your JavaScript programs. Sep 11, 2017 · you could probably look some online material regarding the arrow function and the lexical 'this' context. “ (reading ‘propertyName’)”: This part of the message shows the specific property or method that the code tried to access on the undefined value. So whenever user object will be undefined isManual will be false. Quick Summary Understanding the Aug 31, 2024 · JavaScriptのundefinedエラーの原因と回避方法を詳しく解説。オプショナルチェイニングや非nullアサーション演算子の使い方を含む、エラーを防ぐための実践的なガイドです。 Dec 20, 2018 · This would throw the following error: TypeError: Cannot read property ‘genres’ of undefined I know this is happening because the render method can’t wait for CDM so render will call the state with its default value at least once. Apr 2, 2025 · “Cannot read properties of undefined”: This part of the message tells you that JavaScript attempted to access a property of a value that was undefined. Apr 26, 2023 · TypeError Cannot read property 'id' of undefined is an error that occurs in JavaScript when we try to access a property called 'id' of an object that is undefined or Mar 3, 2024 · To solve the "Cannot read property push of undefined" error, use the `Array. It works by adding the should property to all objects, but if a return value or variable value is undefined, there isn't a object to hold the property. Sep 24, 2024 · Fix 'Cannot Read Property of Undefined' in JavaScript. Table of contents: How to Fix Uncaught TypeError: Cannot read properties of undefined in JavaScript Objects vlogize 13. bar, and sometimes thing. In this way, if typeof myVar is undefined it can't have any property, therefore your if will always fail. Mar 30, 2019 · He might not necessarily be getting an undefined if the data object is created first and the contents are added later. try checking if that is defined first: Jul 22, 2021 · Undefined indicates that a variable has been declared but not assigned a value. filter(Boolean) filters out falsy values (null, undefined, 0, false, '') and avoids Cannot read property of undefined errors. You will (usually) find the keys are being added after your console. Apr 3, 2024 · In conclusion, understanding and handling iteration errors such as "undefined is not iterable cannot read property symbol symbol. Jul 8, 2025 · The JavaScript exception "null (or undefined) has no properties" occurs when you attempt to access properties of null and undefined. Dec 13, 2018 · How to avoid TypeError: Cannot read property ___ of undefined using Array. Or even set a default value for the item property if the input object doesn't contain the property Oct 21, 2019 · 4 Cannot read property 'length' of undefined comes when it is not able to find variable of certain type (In your case a string) to call the function length. /node_modules/vue-loader/dist/index. isArray()` method to check if the value is an array. That is, an object's presence as a key in a WeakMap does not prevent the object from being garbage collected. The " Cannot read property of undefined " error is a common error in JavaScript that occurs when you try to access a property or method of a variable that is undefined. Oct 16, 2019 · How to fix: 'Cannot read property of undefined' of an object instance? Asked 5 years, 4 months ago Modified 5 years, 4 months ago Viewed 312 times The JavaScript Uncaught TypeError: cannot read properties of undefined (reading ‘0’) bug typically occurs when you try to access a property or an index on an undefined object or array. In the context of ‘push,’ it typically arises when trying to add an element to an array that hasn’t been properly instantiated. To avoid the "Cannot read property of undefined" error, ensure that the objects you're accessing are properly defined and initialized. Aug 20, 2025 · Learn how to fix the "cannot read properties of undefined (reading 'map')" error in React with simple coding practices and reliable data handling. querySelectorAll("div"); divs. Nov 13, 2024 · Attempting to Use Methods on Array-Like Objects Some special objects in JavaScript, like DOM node lists, appear array-like but do not have push/pop methods natively: let divs = document. Jun 12, 2023 · In this blog post, I will explain how to resolve a common JavaScript error: TypeError: Cannot read property 'length' of undefined. Instances of Array is an object. stringify(config)) and you will see the keys, or the state of the object at the time you called console. Oct 6, 2022 · By following these guidelines and ensuring that objects are properly initialized and checked for existence, you can resolve the ‘Cannot read property ‘someProperty’ of undefined in Angular’ error and build robust Angular applications. TypeError: Cannot read property 'length' of undefined in Commerce JS when accessing cartWhen Accessing the line_items array of the cart The problem is you are looping through each element of the vocab object starting with "subjects" if it can't find the "word", it can't execute command log because the variable is not defined. A guide on the root cause of 'cannot read map of undefined' as well as techniques and tools to prevent this error. foo. Oct 30, 2021 · TypeError: Cannot read properties of undefined (reading 'name') In order for you to have an idea about what I'm talking about I will share to you some snippets from my code to put you in context. Add a check before to get rid of the immidiate problem, but I'm guessing you're gonna have to investigate why it's undefined for index a as well. js): TypeError: Cannot read property 'styles' of undefined at Object. js (e. On those pages where the function cannot find the id, I receive a "Cannot read property 'addEventListener' of null " error and none of my other functions work. 2. You should simulate a real response object in your tests, e. Apr 19, 2024 · When you call split() on an undefined value, JavaScript throws the "Cannot read property ‘split‘ of undefined" error because undefined is a primitive value that doesn‘t have any properties or methods. The msgArr object doesn't have a property objectID at all, which means it's undefined. Aug 31, 2023 · Experiencing "cannot read properties of undefined JavaScript" errors? This article explains the causes behind this issue and provides effective solutions. Since undefined is not an object type, calling a function or property on such a variable causes the TypeError: Cannot read property of undefined. JavaScript allows you to access properties and methods of an object, but when the object itself is not defined, it results in this error. push("item"); // TypeError: Cannot read property ‘push‘ of undefined The culprit is initializing myArray to undefined instead of starting as an empty Sep 4, 2021 · I have this object defined based on the elements that I retrieved from my HTTP request. Sep 4, 2024 · Javascript cannot read property of undefined: There are three main causes of the “Cannot read property of undefined” error: When we access a property on a variable that holds an undefined value. In your case arrayWord [i]. Uncaught TypeError: Cannot read property 'ConstituentId' of undefined Returning {user. from first. LoginInfo} actually returns an object, but obviously, can't print that to a string. You can use conditional checks to handle situations where an object might be undefined. iterator" is crucial for JavaScript and React developers. Jun 20, 2025 · Cannot read properties of undefined (reading ‘id’) is one of the most common JavaScript errors. That last message should indicate that it is reading map property from an undefined object, if you search in your code there is data. What you need is to access an object in the array, not the array itself. e. Solution: put that baby in a try/catch block: Mar 3, 2024 · The "Cannot read property 'length' of undefined" error occurs when accessing the `length` property on an `undefined` value. What would cause the prop to be undefined when passing from CommentBox into the CommentList? Jun 28, 2025 · Looking for ways to handle Uncaught TypeError: Cannot read property of undefined in JavaScript? This guide will help you to catch errors. May 14, 2017 · And it throws you the error Cannot read property 'words' of undefined You can solve this converting your string to a CryptoJS wordArray, generating the words that it's searching for. so you can set property of an array, for the same reason,you can't set property of a undefined, because its NOT an object Dec 20, 2023 · To comprehend the error, it’s crucial to understand that JavaScript throws this when attempting to perform an operation on an undefined or null value. While for Safari users, you might have received the &#8220;TypeError: undefined is not an object (evaluating &#8230; )&#822 I have some JavaScript code that gives this error: Uncaught TypeError: Cannot read property 'value' of undefined Here is my code: var i1 = document. The problem is that I'm trying to access these elements in the Object Array, I'm getting this 'Cannot read pr Jul 7, 2014 · Uncaught TypeError: Cannot read property 'name' of undefined The userID when alerted gives the same String as ID, but sticking it in the json does not seem to work. The modern solution involves using optional chaining, implementing proper loading states, and adding defensive checks around object property access. Jul 25, 2023 · The TypeError: Cannot read property 'replace' of undefined occurs when the replace() method is called from a variable that has a value of undefined. Sep 13, 2023 · JavaScript Error "Cannot read properties of undefined" can be a common stumbling block for developers, especially those learning the ropes of JavaScript programming on platforms like codedamn. foo is undefined, so it can't access bar). Dec 14, 2023 · TypeError: Cannot read properties of undefined (or null) This means that somewhere in your code, you are trying to access a property (like an object property or method) of a variable that is either undefined or null. Jun 20, 2025 · “Cannot read properties of undefined (reading ‘id’)” typically indicates issues with user data flow, authentication state, or API response handling. so you can set property of an array, for the same reason,you can't set property of a undefined, because its NOT an object Jun 17, 2025 · The 'Cannot Read Properties of Null' error in JavaScript is a common issue, especially when handling DOM elements or null objects. Oct 6, 2013 · 88 This is one of the disadvantages of the should syntax. Oct 2, 2015 · Using JavaScript to split a date and rearrange the format. Feb 19, 2016 · Cannot read property of an undefined object in a IF statement in JEST Asked 9 years, 9 months ago Modified 5 years, 7 months ago Viewed 5k times Aug 28, 2018 · In Javascript, a variable can be assigned a default, in the case that the value unpacked from the object / array is undefined. call() or apply() axios propably does that. , in a browser) and fails to discover the correct global object. Aug 20, 2024 · Defining a variable too early before its value is known Passing undefined as a function parameter value Resetting a declared variable to undefined Take this example that tries to push to an array too soon: let myArray = undefined; myArray. Common Causes: Undefined Variables: Check if the variable you are trying to access is properly initialized. In JavaScript, objects are collections of the properties and if an object is undefined it means it has not been initialized or assigned a value. 2-use (user || {}) when user will undefined that'll use {}. i give it a try. TypeError: Cannot read property 'length' of undefined in Commerce JS when accessing cartWhen Accessing the line_items array of the cart Sep 19, 2022 · Module build failed (from . When we Insert the JavaScript <script/> tag above the HTML, where the DOM elements are Mar 19, 2020 · TypeError: Cannot read property 'data' of undefined - can't access Object "props" beyond certain level in Reactjs Asked 5 years, 8 months ago Modified 5 years, 8 months ago Viewed 15k times Dec 14, 2022 · These types of errors (cannot read property undefined of) mostly occur due to a lack of checking first. This guide explains the causes, how to fix the error with simple checks, and provides tips to avoid it in your code. At the point the console. blur function, however, I then get this error Learn how to use hoisting to prevent JavaScript TypeErrors, like 'Cannot read properties of undefined (reading 'trim')', and how to fix them. In older browsers, you might see this displayed as: “Cannot read property ‘length’ of undefined” Related Errors If you’re encountering similar issues with array or string operations, see these related errors that have common causes: Aug 5, 2025 · The TypeError: Cannot set properties of undefined error is raised when trying to access or modify a property on an undefined object. Since that doesn't exist, there's no way for it to have an includes property available of any type. Jun 6, 2015 · The problem is clearly that state. Jul 3, 2017 · when you know that user can be undefined do two things, 1-Define destruct property default value. you could though generate a function which has a fixed context with . Nov 28, 2019 · The global detection code in var $g = is incorrect when used in ES modules outside of Node. Jul 17, 2023 · This tutorial explains how to fix TypeError: Cannot read properties of undefined (reading '0') in JavaScript Jan 18, 2022 · <p>If you code in JavaScript or you are a web developer, then you must have come across the famous Uncaught TypeError: Cannot read property of undefined on your chrome browser. in javascript if a line of code breaks, the execution will stop. Learn common causes, debugging tips, and solutions to handle errors and improve your code's reliability. log. length is not a proper string for the last condition of your check as there is no element arrayWord [arrayWord. The code below shows the right way to use the split() method on a string type value: Jan 3, 2017 · Asked8 years, 10 months ago Modified 2 years, 7 months ago Viewed 186k times 22 Jan 7, 2020 · Since JavaScript doesn't throw "Array bounds exceeded", you are always safe when you try to access any index - you will get undefined if this element doesn't exist. In older browsers, you might see this displayed as: “Cannot read property ‘id’ of undefined” Related Errors If you’re encountering similar issues with array or string operations, see these related errors that have common causes: Apr 3, 2015 · Uncaught TypeError: Cannot read property '0' of undefined I don't know what to do to say "if it's undefined then don't look into it or something along those lines Nov 20, 2024 · As the docs say, A WeakMap is a collection of key/value pairs whose keys must be objects or non-registered symbols, with values of any arbitrary JavaScript type, and which does not create strong references to its keys. The documentation gives some workarounds, for example: Nov 14, 2024 · In this article, we will explain to you the solutions in detail on how to solve the TypeError: cannot read property ‘push’ of undefined. Jul 11, 2013 · However, be aware of any solution which involves comparing theHref to undefined, which is not a keyword in JavaScript and can be redefined. log(JSON. Date is provided through a json feed as YYYY-MM-DD. Jan 15, 2022 · Cannot Read Property of undefined Object in dependencies array in useEffect or useCallback in React Asked 3 years, 6 months ago Modified 3 years, 6 months ago Viewed 2k times Aug 4, 2015 · The javascript, html and css work in this jsfiddle but when entered into an html file like so: Aug 27, 2024 · In this post we'll be going over how to fix one of the most common errors in JavaScript: 'cannot read properties of undefined'. When we access a non-existent property on a DOM element. Below is the code for the button that opens the menu. it takes in thing. Jun 19, 2025 · Cannot read properties of undefined (reading ‘length’) is one of the most common JavaScript errors. Jul 23, 2025 · Detecting an undefined object property is the process of determining whether an object contains a certain property, and if it does, whether the value of that property is undefined. Dec 17, 2014 · When you use Object. Nov 5, 2024 · Whether you‘re encountering "Cannot read property ‘split‘ of undefined" regularly or just sporadically, this deep dive will help prevent it in the future. length] present in the array. Jul 23, 2021 · One of the most common type errors in JavaScript is the famous "Cannot read property of undefined". Jul 11, 2023 · Are you encountering Cannot Read Property of Undefined Javascript? What does it mean as well as a possible reason why it appears? Oct 11, 2022 · In this article, you have learned how to fix the "Cannot read properties of undefined" error, which occurs when you attach these array methods to variables that are not declared or initialized as variables. See full list on bobbyhadz. Feb 10, 2018 · Cannot read property 'foo' of undefined Most of the times when we're working with JavaScript, we'll be dealing with nested objects and often we'll be needing to access the innermost nested values safely. Apr 16, 2018 · Can't Read JSON - Cannot read property of undefined Asked 7 years, 7 months ago Modified 5 years, 6 months ago Viewed 12k times Dec 29, 2022 · The “cannot read property ‘push’ of undefined” error in JavaScript occurs when you try to call the push() method on a variable intended to contain an array, but actually contains a value of undefined. 6K subscribers Subscribed Aug 3, 2023 · Here, JavaScript calls the addEventListener() method only when the btnEl variable contains a truthy value (a value that evaluates to true) Selector methods return either a null or a valid Element object, so the if block will run only when the variable is not null. " This error typically occurs when you try to access a property or call a method on an object that is null or undefined. Assuming Return Values from Apr 29, 2022 · Another possible reason for encountering the error “TypeError: Cannot read property ‘push’ of undefined” is when the object you are trying to push into is explicitly set to null. map and data seems to be undefined; make sure to validate it before calling map function if it can be possibly null or undefined or even not an array. To avoid deep de-structuring read-only property of an object (which is null), you can assign default values like this. When the element is null, the else block will run, alerting you that the element isn’t found. Sep 15, 2023 · When the error says can't access property "name" of undefined, it's really saying: "Hey, the object you're trying to read name from? Yeah, that one's undefined. The JavaScript Uncaught TypeError: cannot read properties of undefined (reading ‘0’) bug typically occurs when you try to access a property or an index on an undefined object or array. Demystifying the often-misleading "TypeError: can't access property of undefined" in JavaScript. In JavaScript, properties and functions can only belong to objects. defineProperties, by default writable is set to false, so _year and edition are actually read only properties. For a full discussion of checking for undefined variables, see Detecting an undefined object property and the first answer in particular. : Nov 14, 2024 · In this article, we will explain to you the solutions in detail on how to solve the TypeError: cannot read property ‘push’ of undefined. push() is a method of the array object, so you can’t call it from undefined. Oct 8, 2019 · I'm getting "cannot read property 'repeats' of undefined" error, but upon console logging it appears the object (s) is/are well-defined so I don't know why the code is crashing. Jan 12, 2024 · The error, ‘TypeError: Cannot Read Properties Of Undefined (Reading Id)’, generally surfaces when you try to access an ID attribute from an object that isn’t completely defined in your code, a situation that can be resolved by ensuring the object’s correct initiation before referencing its properties. push("a"); // TypeError, not a real array! As mentioned earlier, wrap these cases in Array. Explicitly set them to writable: true: It's telling you that you're trying to access a property on an undefined object. Aug 2, 2023 · The split() method is a method of the String prototype object, so you can only call the method from a string type variable. loader Asked 3 years, 1 month ago Modified 2 years, 11 months ago Viewed 7k times Jul 22, 2021 · Undefined indicates that a variable has been declared but not assigned a value. Aug 14, 2020 · I upgraded my angular application from version 8 to version 10. The error Cannot read property 'map' of undefined' is thrown when the map function in the CommentList component is executed. log call. Aug 13, 2023 · The “Cannot read properties of undefined” error occurs when you try to access a property or call a method on an object that is either null or undefined. " @Kolink it's an old [though terrible] JavaScript convention that an HTML form with a name attribute will be available as a global variable with that name, and inputs with names inside that form will be accessible as named properties of that variable. Oct 5, 2024 · The JavaScript error 'Cannot read property 'X' of null' occurs when you attempt to access a property on a variable that has not been assigned any object reference. filter(Boolean) tl;dr: Array. greens [a] is undefined for a specific index a. Dec 20, 2023 · To comprehend the error, it’s crucial to understand that JavaScript throws this when attempting to perform an operation on an undefined or null value. Now after running ng serve I am getting below one-liner error ERROR in Cannot read property '0' of Mar 11, 2021 · AWS NodeJS SDK V3 DynamoDB UpdateItem - TypeError: Cannot read property '0' of undefined Asked 4 years, 8 months ago Modified 1 year, 9 months ago Viewed 26k times How To Fix 'Uncaught TypeError: Cannot read properties of undefined' - JavaScript Debugging SelfTaughtDev 15. In javascript almost everything is an object, null and undefined are exception. Jul 4, 2019 · It is not the state of the object when you console. bind(yourThisContext) but when you use the arrow function, the this Aug 11, 2023 · The error “cannot read property ‘push’ of undefined” occurs when you call the push() method from an undefined value. Instead, try console. Sep 1, 2022 · Moreover, reading 'map' helps you know which object is it reading. com Jan 14, 2025 · By properly initializing objects, utilizing modern JavaScript features like optional chaining, providing default values, validating function parameters, and avoiding typographical errors, you can effectively prevent and fix this error. They don't have any. Aug 14, 2025 · Fixing TypeError: Cannot Read Property of Undefined in JS: Learn root causes, quick fixes, optional chaining, default values & best practices. getElementById('i1'); var i2 = document. A guide on how to prevent the error "cannot read property '0' of undefined", covering techniques such as try, catch, using const over let, amongst many other Dec 20, 2023 · The “Cannot Read Property ‘0’ of Undefined” error is a common pitfall in JavaScript development, often stemming from attempts to access properties or elements of undefined or null values. Using an optional chaining Jun 25, 2016 · 1 You're returning an object with a property name in your test and you're then trying to access the property data which is undefined. In your case, before accessing the plans array or plans' key (plans[0]), make a computed property or directly apply a condition at the template to check if it is available in the DOM, like this- If you want to loop on all plan items- php Aug 18, 2014 · first check if myVar is undefined, then, once you know it is not undefined, check for its properties. Apr 16, 2018 · Can't Read JSON - Cannot read property of undefined Asked 7 years, 7 months ago Modified 5 years, 6 months ago Viewed 12k times A guide on the root cause of 'cannot read map of undefined' as well as techniques and tools to prevent this error. To get the date, I do: Apr 22, 2017 · Specifically, my dev server was crashing with the Cannot read property 'bar' of undefined type message, and I was like, "what the heck is going on here!?". The problem I have is one of the parameters is a property of a sometimes undefined value of an Object (i. when you use the function keyword, then the function can accept a this context, namely with . Uncaught TypeError: Cannot read property 'Constructor' of undefined If I comment out the protoype. Common Ways This Happens Feb 4, 2021 · An error while overriding '' parameter because of 'TypeError: Cannot read property 'type' of undefined', make sure it follows JavaScript Object Notation (JSON) Aug 5, 2025 · When working with JavaScript, you may encounter the error message "Cannot read property 'click' of null. log happens, data will in fact be an empty object, but dev tools won't actually evaluate the object until you click the arrow to expand the contents.