Vue.js -Most asked interview Questions.

What's Vue.js about? What are its benefits?

Vue is a conceptual platform used to create user interfaces. The main library focuses solely on the view layer and is easy to collect and integrate with other libraries or ongoing projects.

Next are the benefits of using Vue.js.

Low in size — This system is 18 to 21 KB in size and the user does not need time to install and use it.

Easy to understand — One of the reasons for this framework's success is that it's easy to understand. Thanks to its simple structure, the user can easily add Vue.js to his web project.

Easy Compatibility — It is easy to integrate Vue.js with existing applications.

Simplicity — This simplicity also makes it simple for React.js, Angular.js developers, and every other modern JavaScript application to understand.

Virtual DOM — Virtual DOM is used similarly to other existing frameworks such as ReactJS, Ember, etc. Virtual DOM is a lightweight version of the original HTML DOM in the memory tree, and is modified without impacting the original DOM.

Components — Used in VueJS applications for building reusable custom components.

Two-way communication — Due to its MVVM architecture, Vue.js also supports two-way communication, making it very easy to manage HTML block.

Explain the differences between single-way data flow and linking of two-way information?

  • The view(UI) component of the application does not automatically update in one-way data flow when data model changes we need to write some custom code to update it whenever a data model changes. For single-way data flow or binding, v-bind is used in Vue js.

  • The view(UI) part of the software automatically updates when modifying the data model in two-way data binding. In the Vue.js v-model rule, data binding is used in two ways.

What are all Vue's life cycle hooks?

When they are formed, installed and destroyed, each Vue instance passes through series of steps. It will also run functions called life cycle hooks along the way, giving us the ability at a specific point to add our own code. The events below are going through a View case.

BeforeCreate — the development hook's first loop. They allow us to take action before adding our component to the DOM. Inside this we don't have access to the DOM.

Created — You can use this hook to run code after creating an instance. The reactive data can be accessed. Yet Virtual DOM and models have not been installed or rendered yet.

BeforeMount — The beforeMount loop runs right before the initial rendering and after initialization of the model or rendering functions. We're probably never going to need to use this hook.

Mounted — The reactive element, models and rendered DOM will be fully accessible. This is the hook that is most commonly used.

BeforeUpdate — This loop runs on our module after data changes and the update cycle starts. Yet runs immediately before patching and re-rendering the DOM.

Updated — This hook runs on our module and theDOM re-renders after data changes. If after a property change we need to reach the DOM, this is probably the safest place to do it.

BeforeDestroy— This hook runs right before the instance is cut off. This is the right place to do it if we need to clean up incidents or reactive subscriptions.

Destroyed— Use this hook to clean up any last minute.

What's the difference between the instructions v-show and v-if?

Here are some of the main differences between the directives v-show and v-if:

  • v-if only returns the component to the DOM when the expression passes while v-show returns all elements to the DOM and then uses the CSS display property to view / hide expression-based elements.

  • V-if follows guidelines v-else and v-else-if, while v-show does not follow those guidelines.

  • V-if the toggle costs are higher because adding or removing the DOM while v-show has higher initial rendering costs. It means that v-show has a performance advantage when the components are constantly turned on and off, while v-if has an advantage when it comes to initial rendering.

  • V-if supports tab but is not supported by v-show.

Why shouldn't it be used if and for on the same item of directives together?

It is recommended that v-if not be used on the same v-for component. Since v-for has a value higher than v-if. This may be appealing in two common cases:

  • To select things in a list (e.g. v-for="user in usersList "v-if="user.isActive"). Replace users in such situations with a new computed property returning the filtered list (e.g. active users).

  • If it should be secret, stop making a list (e.g. v-for="user in usersList "v-if="shouldShowUsersofList"). In these instances, transfer the v-if to an element of the container (e.g. ul, ol).

What is Vue's $parent?

Similar to $root, a child can access the parent instance using the $parent property.

Although it provides direct access, it makes testing and debugging difficult for the application. So we can't find out quickly where the mutation comes from.

Vue also provides $child as well as $parent, but can be used to access the instance of the child.

What is ref's function in Vue.js?

Despite the existence of props and events, sometimes we can assign a reference ID to the child component using the ref attribute if we still need direct access to a child component. For example:

<base-input ref="usernameInput"></base-input>

What are the VUE.js rules, do you list some of them?

In Vue js, the definition of directive is much simpler than in Angular. The Vue.js specifications provide a way for new attributes and tags to expand HTML. Vue.js has a set of standardized directives that provide expanded functionality for your applications. You can also write your own directives in Vue.js.

Below is a list of widely used Vue.js directives:

  • v-show

  • v-if

  • v-model

  • v-else

  • v-on

Explain lifecylcle of vue instance.

The Life cycle of each Vue instance goes through a series of initialization steps when it is created.

please find the below snap for better understanding .

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