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React Js MCQ's

What the name of React's mixed HTML and JS Syntax?

S React JS

JRE

JPG

MobX

JSX

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A component is basically

S React JS

A let-type variable

A module

A function or a Class

Explanation

 Component can only be a function or a class

A const-type variable

A promise

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What are compomnents properties

S React JS

Props are custom, user-defined component attributes. They can be defined on any component, can have any name and pass any value

Explanation

 Component props are custom attributes that can be passed to a component and accessed inside the component. They look like html attributes, but they are custom-defined.

Props are custom, user-defined component events

Props are component's built-in attributes defined by React itself

Props are read-only descriptors and do nothing special

Props are functions that allow to change component's state

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What will happen if you put some value inside a variable instead of state. This wasn't mentioned, but try to guess!

S React JS

The value inside a variable will not be persisted across component rerenders since every React rerender is unique and not aware of the other ones

Explanation

 Component props are custom attributes that can be passed to a component and accessed inside the component. They look like html attributes, but they are custom-defined.

Props are custom, user-defined component events

Props are component's built-in attributes defined by React itself

Props are read-only descriptors and do nothing special

Props are functions that allow to change component's state

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What React hooks allow us to do?

S React JS

Nothing special. Any custom logic can be written without React hooks and extracted without them.

They enable new feature: custom component attributes

They allow to create custom variable types

They are meant for debugging purposes only

They allow to manipulate the state and hook into lifecycle events

Explanation

React hooks allow to 'hook' into component lifecycle events and state management. Custom hooks (covered in future videos) allow to reuse stateful logic multiple times across multiple components. React hooks are meant to replace class-based components.

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When a components renders on the page, what lifecycle event is triggered?

S React JS

Nothing special. Any custom logic can be written without React hooks and extracted without them.

They enable new feature: custom component attributes

They allow to create custom variable types

They are meant for debugging purposes only

They allow to manipulate the state and hook into lifecycle events

Explanation

React hooks allow to 'hook' into component lifecycle events and state management. Custom hooks (covered in future videos) allow to reuse stateful logic multiple times across multiple components. React hooks are meant to replace class-based components.

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Why do we use Git?

S React JS

Git is a tool for uploading files to github

Git is a storage service for hosting projects.

Git is a tool for managing projects with ease (track files and their changes)

Explanation

 Git is a tool that allows to track all changes to the project folder. It keeps different copies of the project at any stage of the development and allows you to efficiently manipulate file updates. Git is used by every developer in the world

Git is a tool required by Github to be able to upload files

Isn't Github = Git? it's a website.

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Why use Promise.all?

S React JS

Promise.all catches all errors in defined promises

Must be always used when working with multiple promises

To process multiple independent promises concurrently instead of one by one.

Explanation

 Git is a tool that allows to track all changes to the project folder. It keeps different copies of the project at any stage of the development and allows you to efficiently manipulate file updates. Git is used by every developer in the world

Git is a tool required by Github to be able to upload files

Isn't Github = Git? it's a website.

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What is ajavascipt module?

S React JS

JavaScript module is a set of related js files that are grouped together

Javascript module is self-contained js file that does not rely on the global scope.

JavaScript module is a namespace inside global scope that belongs to a js file

Explanation

Promise.all is used when there are multiple independent promises that must be resolved/executed all at once. With Promise_all promises are processed concurrently instead of one by one

Javascript module is an export function inside a js file

JavaScript module referers to a library that is being installed as a dependency

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If one says, that website is written in React. How will you understand this statement

S React JS

a) Uses React to display main pages, b) uses class-based components only, c) Uses jQuery

a) Relies on react as its backend-technology, b) 100% server side rendered c) Uses fiber DOM

JavaScript module is a namespace inside global scope that belongs to a js file

Explanation

JavaScript module isa self-contained js file that does not rely on outer global scope. To share data between modules data must be imported and exported in order to use it

Javascript module is an export function inside a js file

JavaScript module referers to a library that is being installed as a dependency

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