Vue Set Data

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For all object changes that need reactivity use Vue.set(object, prop, value). For array mutations, you can look at the currently supported list here. For vuex you will want to do Vue.set(state.object, key, value). So just for others who come to this question.

It appears at some point in Vue 2.* they removed this.items.$set(index, val) in favor of this.$set(this.items, index, val). Splice is still available and here is a link to array mutation methods available in vue link.

EDIT 1

VueJS can't pickup your changes to the state if you manipulate arrays like this. As explained in Common Beginner Gotchas, you should use array methods like push, splice or whatever and never modify the indexes like this a[2] = 2 nor the .length property of an array.

As stated before - VueJS simply can't track those operations(array elements assignment).All operations that are tracked by VueJS with array are here.But I'll copy them once again:. During development, you face a problem - how to live with that :). push(), pop(), shift(), unshift(), sort() and reverse() are pretty plain and help you in some cases but the main focus lies within the splice(), which allows you effectively modify the array that would be tracked by VueJs.So I can share some of the approaches, that are used the most working with arrays.

You need to replace Item in Array:. Note: if you just need to modify an item field - you can do it just by:. And this would be tracked by VueJS as the item(Object) fields would be tracked. You need to empty the array:. Actually you can do much more with this function splice() - w3schools linkYou can add multiple records, delete multiple records, etc.

Vue.set() and Vue.delete(). Vue.set() and Vue.delete() might be used for adding field to your UI version of data. For example, you need some additional calculated data or flags within your objects. You can do this for your objects, or list of objects(in the loop):.

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And send edited data back to the back-end in the same format doing this before the Axios call:. The Node.js provides a Vue.js data() method to the user.

Basically in vue.js data() we defined collection of logic and stored in component using vue.js we can access data Node.jsassociated with a vue instance.

Components are reusable as many times as per requirement. But each time it uses a separate component and also creates a new instance. When we use a data function at that time each instance maintains a separate copy of the return data object. Most of vue.js uses API to fetch and post data.

It is safe because it does not affect the changes outside the scope. Explanation: The above syntax component is reusable with instance name and notice that when we use data does not provide objects directly.

Instead a component data option is function so each instance is maintaining a separate copy of return data by using the following syntax. We must install Node.js 10.x and above on your system and you can verify by using node –v command in your terminal.

We must install the latest version of Vue on your system. We must install the Vue CLI 3.0 version on your system. We required basic knowledge about Node.js. We required basic knowledge about Vue.js and components. Let’s see how we can implement Vue.js data() with different examples as follows.

Basic example of data method.

Node JS Training Program (3 Courses, 7 Projects)3 Online Courses | 7 Hands-on Projects | 25+ Hours | Verifiable Certificate of Completion | Lifetime Access 4.5 (8,328 ratings).

Related Courses. Vue JS Training (1 Courses, 3 Project)JavaScript Training Program (39 Courses, 23 Projects, 4 Quizzes). In this example, we only made changes in the App.vue file in which we added a data method to access the title.

Illustrate the end result of the above declaration by using the use of the following snapshot. For Data with Method. Explanation: In the above example first we created a data function that returns an object. Every property of vue is added to the vue reactivity system so that if we make some changes in the program that is updated. So that we add title property in our template by using {{}} double curly braces.

Add Items to the Array as Objects

Vue js must require {{}} double curly to pass javaScript Expression. In the second part of the program we have created a method and the method also has an object.

Here we create a Msgmethod which returns a string. Inside the method, we access data object property by using this and finally we added in the template tag. Illustrate the end result of the above declaration by using the use of the following snapshot. Explanation: This is another simple example of data function with methods. Illustrate the end result of the above declaration by using the use of the following snapshot.

Emit data in vue.js with event. Explanation: In the above component, we sent messages from the child component to the parent component. In the above template, we use a button to send the message to the parent component.

See in this template we use the changes function whenever we submit a message to the parent component.

Then we added the following code in the App.vue file. Explanation: In this file actually we are listing our event.

In the first component, we just send messages from the child component to the parent component but in this we actually manipulate them. In this file, we import the HelloWorld.vue component for listening to custom events by using changeMsg function. We also define a setMessage function to handle custom events.

The remaining part is the css part this necessary for design purpose. In this example we by default content of vue.

Illustrate the end result of the above declaration by using the use of the following snapshot. Before Click on Button:. After Submit Message:.

We hope from this article you have understood about the vue.js data. From the above article, we have learned the basic syntax of the vue.js data function. We have also learned how we can implement them in Node.js with examples.

From this article, we have learned how we can handle vue.js data as well as components in Node.js.

This is a guide to Vue.js data() Here we also discuss the definition and how data() works in vue.js along with different examples and its code implementation.

You may also have a look at the following articles to learn more –.

Binding a class on an item and controlling it by the truthy value of a data property is a powerful feature of Vue.js. I will look at a few different ways to do this from binding a class to one item to binding a class to many items at the same time while looking at how it works under the hood.

To start I will look at the problem I encountered and to finish up look at how versatile what we just learnt is. When I tried to add a class to a list item in Vue.js to highlight a selected item, only one item could be checked at a time and an item could not be unchecked either.

See below for what I am talking about. See the PenBasic Vue.js Todo App by Simon (@simonramsay) on CodePen. This was fine when adding an item or deleting an item but not the intended outcome when checking something off.

Being able to have many items checked off at the same time is what was needed. In this post, I will guide you through the steps to my solution and try to explain it as clearly as possible.

Setting up our App

In the below app that I made we have a simple input that when you press enter, on key up a task is added to the tasks array in the data property of our Vue instance.

I also used the same code snippet to delete the tasks by passing the index into the method and using splice(). See the PenBasic Vue.js Todo App by Simon (@simonramsay) on CodePen. So the next job was to enable a user to check a task off as completed. I added a v-bind directive to bind the class completed to the li items and created a data property.

Well that could be confusing, let's fix it

What this does is it binds the class if the value of the data property is true. Check Class and Style Bindings on Vue.js official site for more information. In this case, if the completed button is clicked the data property completedClass is set to the index of the item.