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Questions and Answers
What must be true about the keys assigned to elements in a list?
What must be true about the keys assigned to elements in a list?
What is a major issue with using array indexes as keys in React?
What is a major issue with using array indexes as keys in React?
How does the method of assigning keys to components compare to props in React?
How does the method of assigning keys to components compare to props in React?
When should keys be assigned when using the map() function in React?
When should keys be assigned when using the map() function in React?
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What is a good practice for choosing keys for items in an array in React?
What is a good practice for choosing keys for items in an array in React?
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What is the purpose of the constructor() method in a React component?
What is the purpose of the constructor() method in a React component?
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What are the three main phases of a React component's lifecycle?
What are the three main phases of a React component's lifecycle?
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What is the correct method to create a connection to a MySQL database in Node.js?
What is the correct method to create a connection to a MySQL database in Node.js?
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Which React lifecycle method is called last during the Mounting phase?
Which React lifecycle method is called last during the Mounting phase?
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What does getDerivedStateFromProps() primarily accomplish?
What does getDerivedStateFromProps() primarily accomplish?
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Which of the following statements accurately describes an Auto Increment primary key?
Which of the following statements accurately describes an Auto Increment primary key?
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What will be the output if the 'CREATE TABLE customers' command executes successfully?
What will be the output if the 'CREATE TABLE customers' command executes successfully?
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Which method must be included in every React component for it to render?
Which method must be included in every React component for it to render?
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In the example with events, what callback function is executed when the 'open' event is fired?
In the example with events, what callback function is executed when the 'open' event is fired?
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What happens in the constructor() method after calling super(props)?
What happens in the constructor() method after calling super(props)?
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What should be included when creating a .js file to handle events in Node.js?
What should be included when creating a .js file to handle events in Node.js?
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In the provided code, what would the output display when rendering the components?
In the provided code, what would the output display when rendering the components?
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Which data type should the primary key column be defined as in order to use AUTO_INCREMENT?
Which data type should the primary key column be defined as in order to use AUTO_INCREMENT?
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Which of the following statements about the Mounting phase is true?
Which of the following statements about the Mounting phase is true?
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What is the purpose of the 'mysql.createConnection()' function in the MySQL example?
What is the purpose of the 'mysql.createConnection()' function in the MySQL example?
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In Node.js, which statement is true regarding events?
In Node.js, which statement is true regarding events?
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What does the render() method do in a React component?
What does the render() method do in a React component?
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When is the componentDidUpdate method triggered?
When is the componentDidUpdate method triggered?
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What is the purpose of the componentWillUnmount method?
What is the purpose of the componentWillUnmount method?
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Which of the following best describes React Hooks?
Which of the following best describes React Hooks?
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What is one of the rules of using Hooks?
What is one of the rules of using Hooks?
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What version of Node is required to use React Hooks?
What version of Node is required to use React Hooks?
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In React, which of the following statements about useState() is true?
In React, which of the following statements about useState() is true?
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Which of the following tools is necessary to run a React app with Hooks?
Which of the following tools is necessary to run a React app with Hooks?
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What is the purpose of the app.get method in an Express application?
What is the purpose of the app.get method in an Express application?
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What will happen when the following curl command is executed: curl -X POST http://localhost:3000/hello?
What will happen when the following curl command is executed: curl -X POST http://localhost:3000/hello?
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What function is used to handle all types of HTTP methods at a particular route in Express?
What function is used to handle all types of HTTP methods at a particular route in Express?
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In the context of Express, what does the app.use function do?
In the context of Express, what does the app.use function do?
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Which file should be created to separate the routes from the main index.js file?
Which file should be created to separate the routes from the main index.js file?
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What is the expected response when visiting the route localhost:3000/things/?
What is the expected response when visiting the route localhost:3000/things/?
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How does Express differentiate between HTTP methods at the same route?
How does Express differentiate between HTTP methods at the same route?
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What is the correct way to export the router defined in things.js for use in index.js?
What is the correct way to export the router defined in things.js for use in index.js?
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Study Notes
Connecting to MySQL with Node.js
- Define the name of the database in the
mysql.createConnection
object. - Use the
con.connect
method to establish a connection to the database. - The
con.query
method is used to execute SQL queries on the database.
Creating Tables
- Use the
CREATE TABLE
statement to create a new table in the database. - Specify the table name and define the columns with their data types.
- Include primary key column for unique identification.
Primary Key
- Primary key is a unique key for each record in the table.
- Use
INT AUTO_INCREMENT PRIMARY KEY
for primary key column that automatically increments for each new record.
Node.js Events
- Events represent actions on a computer, like connection establishment or file opening.
- Node.js objects, such as
readStream
, can fire events during operations. - The
Events
module provides methods for creating, firing, and listening to custom events.
Keys in React
- Keys are used to uniquely identify elements in a list within a React component.
- Keys help React track changes and efficiently update the virtual DOM.
- Keys should be consistent and unique within a list, but not necessarily globally unique.
Lifecycle of React Components
- React components have a lifecycle with three main phases: mounting, updating, and unmounting.
- Each phase has specific methods that get called during the component's lifecycle.
Mounting
- Mounting refers to adding elements to the DOM (Document Object Model).
- The following methods are called during the mounting phase:
-
constructor()
: Initializes the component's state and other initial values. -
getDerivedStateFromProps()
: Sets the component's state based on the initial props before rendering. -
render()
: Renders the component to the DOM. -
componentDidMount()
: Executes after the component is added to the DOM.
-
Updating
- Updating occurs when the component's state or props change, requiring the component to re-render.
- The following methods are called during the updating phase:
-
getDerivedStateFromProps()
: Updates the component's state based on changes to props before rerendering. -
render()
: Rerenders the component to reflect the updates. -
componentDidUpdate()
: Executes after the component is updated in the DOM.
-
Unmounting
- Unmounting occurs when a component is removed from the DOM.
- The
componentWillUnmount()
method is called before the component is removed.
Hooks
- Hooks enable you to use React features like state and lifecycle methods within functional components.
- Two main rules for hooks:
- Only call hooks at the top level of a React function.
- Only call hooks from React functions.
useState() Hook
-
useState()
hook provides state management within functional components. - It returns an array containing the current state value and a function to update the state.
Express (Node.js Framework)
- Express is a popular web framework for Node.js that enables creating web applications.
- Use
app.get('/hello')
to handle GET requests for the/hello
route. - Use
app.post('/hello')
to handle POST requests for the/hello
route. - The
app.all('/test')
method manages any HTTP method for the/test
route. - Use Express Router (
express.Router
) to separate route definitions into separate files for better organization.
Middleware in Express
- Middleware functions are executed before the request is sent to the route handler.
- Middleware can modify the request or response object or perform authentication or authorization.
- Middleware can be defined using
app.use()
for specific routes or globally for the application. - Middleware can help with error handling, logging, and authentication.
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Description
This quiz covers the essential aspects of connecting to MySQL using Node.js. It includes creating database connections, executing SQL queries, and understanding primary keys. Additionally, it touches on handling events in Node.js and the usage of keys in React.