Arrow functions not working in vue. js with TypeScript for robust web development.

Arrow functions not working in vue Mar 13, 2017 · The first is to use an ES6 arrow function, because these functions bind the this of the scope in which the function is declared. Also, why does it need to be a non-arrow function in the second example Because this is the only way the function can get component instance as this. Here are some tips by Jacob Bennett. debounce itself is called when it's called. Under the hood, Vue compiles the templates into highly-optimized JavaScript code. Because of this, it might be a good habit to always keep them: Then, when we listen to the event in the parent, we can use an inline arrow function as the listener, which allows us to access the event argument: Oct 1, 2018 · Functions With Dynamic Context The last situation where arrow functions can get you in trouble is in places where this is bound dynamically. Includes examples and code snippets. 5 tl;dr In general, arrow functions work in event handlers (doesn't mean that you should use them, see below). js training from core team members & industry experts. activeEntry will not work unless you rewrite using the arrow function: May 5, 2020 · According to the Vue docs, "you should not use an arrow function to define a watcher". Although it is shorter and faster to type, its power comes from how it defines its scope. Therefore attempting to assign this. Suddenly, the arrow Many Vue patterns involve passing data from a parent component to its children using props. Maybe your API response handler couldn't access this. If you use arrow functions in these locations, that dynamic binding will not work, and you (or someone else working with your code later) may get very confused as to why things aren't working as expected. Note that you should not use an arrow function to define a watcher (e. In-depth lessons with weekly updates on Pinia, Typescript, Vue Use, Laravel, & more Jun 24, 2025 · Learn how to use Vue refs and lifecycle methods for managing focus and improving keyboard accessibility in your Vue applications. Mar 4, 2025 · If you’re a Vue. So yeah, don't worry about using traditional functions, especially if you can explain the why's behind your choice. This can simplify working with arguments in nested functions. For most uses cases changing an anonymous function is fine and will work as expected but not always. Let's dive into an example where a render() function would be practical. Jun 29, 2023 · I've looked through the other posts in the forum, but still cannot get this working in my Excel for some reason. A workaround for this issue is to manually disable symlinks resolution in webpack: Oct 19, 2024 · Mastering Arrow Functions in JavaScript: Common Pitfalls to Avoid JavaScript has evolved significantly over the years, and one of the most transformative features is the introduction of arrow functions in ES6 (ECMAScript 2015). About the usage of render functions, to generate attributes, use attrs, not props. The first is a string, which can be Jun 24, 2025 · Learn how JavaScript arrow functions work with syntax shortcuts and how they handle this compared to regular functions. Don't worry, you're not alone — I've run into this issue countless times, and I'll show you just how to solve it. The likely cause of this is that you're mixing up your usage of regular functions and arrow functions. Jan 1, 2016 · I don't believe that a computed property in Vue. js can accept an argument, they are supposed to be able to build themselves without additional interaction. Rest assured - since all Vue handler functions and expressions are strictly bound to the ViewModel that’s handling the current view, it won’t cause any maintenance difficulty. js computed properties not working with arrow functions. For instance when adding a function to an class dynamically via Object. Jun 3, 2020 · I have create a new Vue sample, it seems that after install babel or the @babel/plugin-transform-arrow-functions, it could use the arrow function in the components without using the "transpileDependencies" option. My guess would be that either CopyPlugin or DefinePlugin is expecting something to be in scope that is not in the scope that the arrow function is bound to. Jan 12, 2021 · Since arrow functions are bound to the parent context, this will not be the Vue instance as you’d expect, often resulting in errors such as Uncaught TypeError: Cannot read property of undefined. Writing Vue modules and using ES6 features can improve and clean up your code. Read more Feb 17, 2020 · Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. If we were writing regular old ES6, outside of a Vue component, we'd probably want to turn that into an arrow function. But that event listener is not removing at all. addEventListener`. If you are using vue 3 with script setup, use Volar only, (you can deactivate vetur for the workspace) Learn how to handle events in Vue. Render Functions & JSX Basics Vue recommends using templates to build your HTML in the vast majority of cases. Imagine working on an important project on your Windows PC, utilizing keyboard shortcuts to switch windows, snap apps into predefined regions, or navigate between applications swiftly. this is then not bound to the Vue instance but the parent (Window) which causes it not to work. The rule should detect when a component uses an arrow function inside the watch section. Learn what a malformed arrow function parameter list is and how to fix it with this comprehensive guide. Getters are exactly the equivalent of computed values for the state of a Store. Let's look at another example: Mar 2, 2019 · As arrow functions are bound to the parent context, this will not be the Vue instance as you’d expect and this. My guess is that you're using an arrow function. If you switch out your arrow function for a regular function the scope is bound correctly: Dec 1, 2019 · While Vue Composition API RFC Reference site has many advanced use scenarios with the watch module, there are no examples of how to watch component props. Rule Details This rule can enforce or disallow the use of braces around arrow function body. So when we click it, the div shows since show becomes true . Say you want This rule disallows using arrow functions when defining a watcher. Inside a traditional function called by setTimeout, however, this refers to the window object (which is why you ran into errors when you tried to access this. Recently when refactoring a Vue 1. Two main characteristics of Vue props There are two specific things to keep in Sep 12, 2022 · The keyword this loses it's context inside of new IntersectionObserver() without the use of an arrow function. 0bug]Important!!! why vue 2. I do not use arrow function in vue component as I find it troublesome. Can you just use arrow functions for everything? Does that ruin anything? I know it has something to do with the scope of "this" or starting up right away or something. Dec 18, 2018 · Arrow function does not bind data with axios response Asked 6 years ago Modified 6 years ago Viewed 1k times Mar 9, 2022 · Learn how to use JavaScript arrow functions, understand fat and concise arrow syntax, and what to be aware of when using them in your code. Arrow functions are always Jest/Vue test utils - How to test functions are called when key is pressed? I have an event that added using `onMounted ()` method using `window. Apr 8, 2022 · The problem that you're running into is not due to "how keydown and change events work together in Vue. Sep 23, 2022 · Arrow function bind to the scope they are in. js import Vue from 'vue'; import HelloWorldCompon Jul 15, 2016 · This works because the this of arrow functions is bound to the this of its enclosing scope - in Vue, that's the parent/ enclosing component. Dec 12, 2020 · I'm not able to reference my data fields in my Vue 3 methods because of some misunderstanding in syntax and scope. * To create a state, go to the arrow function inside the defineStore and create a const. Assign the ref method to the created const. Arrow functions are a syntax introduced in Ecmascript 2015. They may be defined with a block body (denoted by curly braces) () => { } or with a single expression () => , whose value is implicitly returned. In Vue, until recently, all the functions were declared inside the methods option, which made this debate irrelevant. You shouldn't use arrow function. 5? why vue 2. Aug 30, 2019 · Because in arrow function this no more points to the Vue instance, and they have their own context this. See here for more details. name to access the value in props? that how it is defined by the Vue API. js over the past year. 1. Instead, they inherit the arguments object from the enclosing non-arrow function. Nov 20, 2019 · As arrow functions are bound to the parent context, this will not be the Vue instance as you’d expect and this. const squareIt = x => x*2; Here, it evaluates x*x and returns it. js per se, but rather is a basic underlying issue with HTML and JavaScript. js", and actually has nothing to do with Vue. That's where we can use the render function. Oct 14, 2016 · need repro on Oct 13, 2016 yyx990803 changed the title [2. updateAutocomplete (newValue)). this is bound to the object you are defining it in, not the instantiated Vue instance. In our case, we need an array to store objects. VS Code provides two powerful commands to navigate in and across files with easy-to-use keyboard shortcuts. So, in your Sep 12, 2018 · vue-cli@3 with babel@7 not coverting arrow functions under node_modules #2500 Jun 24, 2025 · Windows + Arrow Keys Stops Working: Troubleshooting, Causes, and Solutions for Seamless Navigation In the landscape of modern computing, efficiency and smooth user experience are critical. Jun 29, 2021 · It seems arrow functions are bound to the parent context. Arrow functions have two syntactic forms for their function bodies. That's not the only special behavior they have, please refer to the MDN documentation for more information. Let’s actually see this by logging this to the console. js We can use setTimeout with Vue. Functions are the basic building block of any application, whether they’re local functions, imported from another module, or methods on a class. You should avoid using arrow functions when defining methods, as that prevents Vue from binding the appropriate this value. Render Functions Vue recommends using templates to build applications in the vast majority of cases. I believe that your fault was that you wrote a method and then tried to register it as a computed property. Hopefully, this guide can save you some time! Jan 24, 2018 · Side note: Declaring an arrow function inline inside a render method will break a PureComponent because every time your component renders it has to declare a new anonymous function, so the shallow props comparison that a PureComponent does is broken by this and will always re-render. I Dec 13, 2018 · Yes, note that Vue's data is a function and not an object. However, clicking the button only leads to the error message: Uncaught Error: vue-query hooks can only be used inside setup () function. Discover setup, best practices, and optimization tips in this comprehensive guide. Aug 23, 2020 · Not too bad, but a bit verbose. Options The rule takes one or two options. When using the old way of defining functions the this scope does not work the May 25, 2020 · 2 I have a Vue application which should work in a ES5 Browser (iOS 9). 3. The same would happen if you were to define methods using an arrow function. Every guard function receives two arguments: to: the target route location in a normalized format being navigated to. I understand the differences between arrow/non-arrow functions, but I'm not sure about the "Vue magic" and how it might play into things. Is there any particular reason to declare functions with arrow syntax instead of the "function" keyword when using the composition API in Vue 3? I've noticed the examples of the documentation use arrow functions. Let’s dive into a simple example where a render function would be practical. Why Ctrl + Arrow Functions Matter When working in Microsoft Excel or Word, navigation shortcuts like Ctrl + Up Arrow or Ctrl + Down Arrow can dramatically speed up your workflow. Using an arrow function in your then and catch handler's ensures that 'this' remains a reference to the Vue instance. from: the current route location in a normalized format being navigated Jan 18, 2019 · @TylerRoper i'm not clear on: 1) how arrow function inside the getter takes the value, isn't it just the name of a parameter? 2) as I saw in the console this getter returns function what I don't understand is how it works in the if statement, the console was always returning true no matter what mock object with inventory properties I used but outside console it works perfectly fine . Feb 10, 2025 · Arrow Functions (Concise Syntax) Arrow functions are a more concise way to write functions in JavaScript. Use arrow functions inside components ES6 introduced a new way to define functions. Sep 25, 2021 · Arrow function not working Anyone would know why if i use an arrow function instead of an anonymous function declaration, the callback inside de eventlistener will not run? See below for code: //this works We would like to show you a description here but the site won’t allow us. The following code defines an arrow function that takes two numbers and returns their sum. Vue uses an HTML-based template syntax that allows you to declaratively bind the rendered DOM to the underlying component instance's data. And to: Why I need to write this. There are situations however, where you really need the full programmatic power of JavaScript. So it should be a simple fix to just change the registration of your function from computed to methods which it really is. Apr 8, 2014 · It is an advantage, but it can also be a limitation if you plan to reuse the function outside the original context. g. 0. They don't have their own this binding. I'm using Typescript. With function keyword you can make a function literal that will hoist and function expression that will not. component? evolutionxbox – evolutionxbox 2021-03-12 15:02:52 +00:00 CommentedMar 12, 2021 at 15:02 However, when you are working on a task, you will find yourself quickly jumping between the same set of files. While arrow functions provide a cleaner syntax and solve several common issues related to the handling of this, they also come with their own set of challenges. Say you want Composition API setup () Basic Usage Accessing Props Setup Context Usage with Render Functions Global before guards are called in creation order, whenever a navigation is triggered. js by passing in an arrow function as an argument into it. js using vscode i get an unexpected formating. 📖 Rule Details This rule disallows using arrow functions when defining a watcher. But what if we need a child to affect its parent? Using emit, we can trigger events and pass data up the component heirarchy. Will arrow functions not work properly in some cases? Feb 10, 2017 · If you try to make use of ES6 arrow functions within the methods object, you will not be able to access other methods or data properties. 5? on Oct 13, 2016 I never know what I'm supposed to use so I use arrow functions for everything but when im halfway through a project and stuff starts not working I end up making it worse trying to change around the function syntax. That means the arrow function version: Note Arrow functions must be defined before they are used. Sep 30, 2017 · When building a Vue project including arrow functions, webpack's UglifJsPlugin gives this error: Unexpected token: operator (>) example: app. Oct 29, 2018 · The issue comes from the lexical scope of the arrow function you define within _. Auto-complete As we discussed earlier, when a module provides named exports, we can easily select a specific function from the module by using a shortcut provided by the IDE. Jan 6, 2022 · When I write arrow functions in Vue. Neither is it mentioned in Vue Composition Learn how to define and use actions in Pinia, a type-safe and flexible Vue store, to handle complex logic and asynchronous operations. Jun 6, 2019 · Certainly you can use arrow functions deliberately to override this behavior, but especially in the cases of jQuery and Vue this will often interfere with normal functioning and leave you baffled why code that looks the same as other code nearby is not working. So my questions are: 1. You can only omit the return keyword and the curly brackets if the function is a single statement. They’re also values, and just like other values, TypeScript has many ways to describe how functions can be called. . In fact, there are several benefits in using v-on: It’s easier to locate the handler function implementations within your JS code by skimming the HTML template. Hence you should use function instead. It is not yet supported but all modern browsers, so only use it if you are targetting a browser you know supports it, or if you are compiling your javascript down to ES5 syntax using something like babel. Vue ES6 Conventions Use method definitions for all “top level” methods. In other words, it's not always the same value (although it it is in this example). vue setup: () => { function goPrevChannel() { Jul 29, 2024 · Arrow functions do not have their own arguments object. I wanted to handle ctrl+period keyboard events and it took me forever to find the part of the documentation that addressed my use case. Note that the context binding will not work if you use an ES6/2015 arrow function, as they implicitly bind to their parent scope. I understand the differences between the two types of functions with the main difference being that `this` is resolved lexically. Try making that a method of your component. Props work in a very similar way to this. What I mean by 'limitation' is that changing the value of this is something you can do with regular functions but not with arrow functions. Just like all other properties of the component instance, the methods are accessible from within the component's template. With arrow functions, you don't need to bother with all these different subtleties. Aug 29, 2022 · Learn how to correctly type an arrow function parameter in a Vue 3 attribute and understand the process of typing a Vue component. Jan 5, 2025 · This article explores how to work with functions and methods in Vue 3 using both approaches and highlights their differences. Let’s learn about how to write types that describe functions. This is useful for things like: emitting data from an input closing modals from inside the modal itself making our parent component respond to one of its children How does Vue Jun 20, 2017 · You can read more in the Mozilla documentation on arrow functions. js developer, you’ve probably encountered situations where this didn't behave the way you expected. myMethod will be undefined. Expected: <input type May 20, 2025 · Learn how to integrate Vue. This rule disallows using arrow functions when defining a watcher. The code inside function() {} is called after a delay when debounced function is called. Oct 3, 2018 · Certainly you can use arrow functions deliberately to override this behavior, but especially in the cases of jQuery and Vue this will often interfere with normal functioning and leave you baffled why code that looks the same as other code nearby is not working. Some of the functions in Vue components are transformed to Arrow functions: ()=> which breaks iOS9 Safari. Jan 10, 2024 · However, with default exports, this isn't possible. Oct 8, 2018 · 1 This question already has answers here: Use arrow function in vue computed does not work (6 answers) Nov 22, 2019 · This line is not working, why? window. updateAutocomplete will be undefined. Sep 26, 2023 · To fix Vue. Several tutorials use arrow functions in their `script setup` and composables. I know this question has been asked to death but I can't for May 17, 2021 · You need to use a regular function syntax when declaring a method, and an arrow function in any nested . If still not working, can you post the Enough code to reproduce the problem as in Minimal, Complete, and Verifiable example. In Vue 3, you can define functions using traditional JavaScript syntax or the modern ES6 arrow functions. But, first, your example code int the question wouldn't work: Check out some examples on how to improve your code with ES arrow functions. We cover how to use parameters, reference data properties and issues with arrow functions and function references. But there are a couple rules you need to know about first. In this lesson, we’ll learn how to use ES6 arrow functions. The reason is arrow functions bind the parent context, so this will not be the Vue instance as you expect and this. You could have a try. Hopefully, this article helps narrow down the problem so we can get it solved! I use arrow functions only, so it's not the problem. Technically, you can also use data to pass a function to the template, but I wouldn't recommend it. then's. We pass props to another component, and that component can then use that value. Hold Ctrl and press Tab to view a list of all files open in an editor group. And i don't really understand why some are transformed correctly and some not. It's not about the keyword, but how you use it. It is because webpack resolves symlinks to their real locations by default, thus breaks ESLint / Babel config lookup. All Vue templates are syntactically valid HTML that can be parsed by spec-compliant browsers and HTML parsers. target keywords. prototype. Instead, this is looked up in scope just like a normal variable. Mar 9, 2018 · Click here to share this article on LinkedIn » Here are a couple of tips that I have learned from working with Vue. data, or your map Nov 4, 2025 · Exploring why arrow functions break 'this' context in Vue computed properties and alternative solutions using standard functions or context access. debounce. This is because arrow functions are bound to the parent context, and therefore the this keyword will not refer to the Vue instance as you would expect. this show be the component instance since arrow functions don’t bins to their value of this . They can be defined with the getters property in defineStore(). We set setShow as the value of the @click directive to run it when we click the button. Ctrl + left arrow or right arrow works, Symbolic Links in node_modules If there're dependencies installed by npm link or yarn link, ESLint (and sometimes Babel as well) may not work properly for those symlinked dependencies. Write cleaner TypeScript arrow functions with proper type annotations and learn when to use them over traditional function declarations. 0 not working on ios 9. Use arrow functions for any callbacks inside “top level” methods. May 19, 2021 · Use setTimeout with Vue. How to test that my method goPrevChannel () or goNextChannel () are called when I press `arrow down` or `arrow up` key? Component. props. When do you not use an arrow function? Remember, when using an arrow function this is not bound to anything and it just inherits it from the parent scope which in this case is the window. name instead of this. Jan 24, 2022 · export function increment() { // the variable 'count' will not be found if the increment function is defined outside the store and then imported to the store: count. Aug 21, 2018 · The context is the one of the closest enclosing function ion which the arrow function was created, or if there is none then the global context. In this article, we’ll look at how to fix Vue. target). Learn how functions work in Vue. That’s where you can use the render function, a closer-to-the-compiler alternative to templates. Not that it wouldn't work, but Vue makes anything declared in data reactive and there's no point in making a function (which is basically a constant) reactive. searchQuery: newValue => this. value++ // this problem will apply to any other variable (state, action, or getter) } How Do I Fix My Keyboard Arrow Keys Not Working? If you're dealing with your arrow keys not working on your keyboard, there are quite a few different fixes you can try out to get them back in working order. dev’s front-end. That was the reason my code did not work. js with TypeScript for robust web development. That means you don't have to call . However, there are situations where we need the full programmatic power of JavaScript. 3 Don't use arrow functions in the render declaration. They receive the state as the first parameter to encourage the usage of arrow function: SlivaNilow commented Aug 5, 2020 Describe the bug in ie 11 not working arrow function Feb 15, 2017 · Note that you should not use an arrow function to define a watcher (e. bind. Say we want to generate anchored headings: Feb 16, 2020 · For the arrow function, there are two ways you can return a value, implicitly and explicitly. Nov 29, 2013 · How to refer to the correct this Use arrow functions ECMAScript 6 introduced arrow functions, which can be thought of as lambda functions. Inside the function we can access that value as message. They are defined using the => syntax and have implicit returns for single expressions. Arrow functions are suitable as expressions as they do not have their own bindings to the this, arguments, super or new. myMethod is not a function. Oct 22, 2020 · Since an arrow function doesn’t have a this, this will be treated as any other variable and lexically looked up through parent scopes until found, often resulting in errors such as Uncaught TypeError: Cannot read property of undefined or Uncaught TypeError: this. I wish to change the settings for Prettier when auto formating arrow functions in vscode. Dec 19, 2020 · 4 Inside a template you can use functions defined as methods or computed. Sep 24, 2023 · Sometimes, we want to fix Vue. Feb 10, 2017 · That’s because arrow functions are bound to the parent context, and therefore this will not be the Vue instance as you would expect. This feature not only saves time, but also helps the IDE suggest and auto-import the necessary functions as we type. Arrow functions are not hoisted, so you have to initialise it before calling but normal functions can be called before initialisation. There are a number of ways to fix arrow keys if they stopped working. Example: This is a part from a vue component: data() { return { birthday: '', accepted This rule disallows using arrow functions when defining a watcher. Jun 18, 2023 · If you’ve spent more than 5 minutes with the language, you already know that. Also, quoting the Render Functions & JSX docs: There is no direct v-model counterpart in render functions - you will have to implement the logic yourself. Below demos of how that could be achieved. If you don’t provide a code block (no open curly brace) and it’s just an expression, the arrow function will just return whatever that expression evaluates to. Actions: These are named functions which are used to ** modify ** *a state’s property or perform an action through or with the state. this in an arrow function is bound to the value of this in lexical scope where the arrow function is defined; whereas when an arrow function is called, this may be dynamically bound to another value, as explained in other answers. Mar 12, 2021 · Then works with both "normal" and arrow functions? I'm assuming you might be forgetting to return in the normal function as arrow functions (without the curly braces) return implicitly? Try return module. Basic to advanced Vue. From the Mozilla documentation: An arrow function expression (also known as fat arrow function) has a shorter syntax compared to function expressions and lexically binds the this value (does not bind its own this, arguments, super, or new. js computed properties not working with arrow functions, we should replace arrow functions with regular functions so that this is set to the Vue component. Not always. I wrap useQuery inside the arrow function to pass variables , and the function is to be triggered by button via v-on. Function Type Expressions The simplest way to describe a function is Here we pass the variable myMessage into the function as the argument message. That will actually work, because that’s a full on function, and not an arrow function. removeEventListener("scroll", handler, false); I tried all approaches: arrow function, function declaration, etc. Arrow functions are a syntactically compact alternative to regular function expressions. When you use the this keyword inside an arrow function you're referring to the this of either a surrounding regular function/method or the global object if there is none. Guards may be resolved asynchronously, and the navigation is considered pending before all hooks have been resolved. One of the hardest topics to explain to a non front-end engineer is a function expression and the whole idea of functions being first-class citizens. You can read about it here. js, a progressive JavaScript framework, with this comprehensive guide on event handling essentials. Arrow functions bind to their parent context, which means they will not have access to the Vue component instance via this. However, inside our component the following code wouldn't work: Aug 3, 2023 · We’ve to use an arrow function to get the right value of this in the callback function. Sep 4, 2022 · I recently spent far too long fighting with Vue’s keyup and keydown functionality while building Boot. 0 application, I utilized ES6 arrow functions to clean up the code and make things a bit more consistent before updating to Vue 2. In this Render Functions & JSX Basics Vue recommends using templates to build your HTML in the vast majority of cases. Apr 23, 2021 · The really important takeaway here is that arrow functions do not have their own this. To do this, all I need to do, is to remove the function keyword and add an arrow, represented by an equals and a greater than symbol. Writing Functions in Vue 3 Functions are reusable blocks of code that return a value or perform an operation. updateAutocomplete(newValue)). So let’s do the same thing with an OG function: There we go. Sep 25, 2025 · Arrow functions in JavaScript are a concise way to write functions using the => syntax, automatically binding this from the surrounding context. Mar 11, 2022 · This is what happens in case of debounce. basketAddSuccess in that context). You are facing this error because an arrow function wouldn't bind this to the vue instance for which you are defining the computed property. tmlww xnpwrad ojfeje qwgef dkgvap nml slrs vyez czisns qxp rnctmm neo iobu jncg eqdrlu