You are maintaining a server that has strict security requirements. You need to allow cross-origin requests but with stringent restrictions. How can you implement CORS to fulfill these requirements while maintaining security?

Set Access-Control-Allow-Origin to * and rely on server-side authentication.
Implement preflight requests with custom headers and allow only authorized clients.
Avoid using CORS and handle cross-origin requests through server-side scripting.
Enable CORS for all origins and use server-side IP filtering.

To implement stringent security with CORS, you should use preflight requests with custom headers to allow only authorized clients. Option A is not secure as it allows any origin. Option C suggests avoiding CORS altogether, which may not be practical. Option D relies on IP filtering, which can be bypassed.

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To install all the dependencies listed in the package.json file, the ______ command should be used.

npm init
npm add
npm install
npm create

To install all the dependencies listed in the package.json file, you should use the npm install command. It reads the dependencies specified in package.json and installs them. The other options are not used for this specific purpose.

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In Sequelize, which method is commonly used to find a single instance from the database?

findAll()
findOne()
findSingle()
fetchOne()

In Sequelize, the commonly used method to find a single instance from the database is findOne(). This method retrieves the first matching record that meets the specified criteria. The other options, findAll(), findSingle(), and fetchOne(), do not represent the standard method for retrieving a single instance in Sequelize.

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In JavaScript, a for…in loop is used to iterate over the ________ of an object.

properties
values
methods
variables

In JavaScript, a for...in loop is used to iterate over the properties of an object. It is commonly used for object iteration, and it iterates through the keys or property names of an object.

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Which of the following is the correct way to declare a variable in JavaScript?

var x = 10;
x := 10;
int x = 10;
declare x = 10;

In JavaScript, variables can be declared using the var keyword. The other options are either used in different programming languages or are not valid syntax in JavaScript.

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In which of the following template engines can you write plain JavaScript code inside special tags?

Mustache
Handlebars
Pug
EJS (Embedded JavaScript)

EJS (Embedded JavaScript) allows you to write plain JavaScript code inside special tags <% %> or <%= %>. This feature is useful for executing JavaScript logic and generating dynamic content within templates. Mustache, Handlebars, and Pug have their own template syntax and do not support this feature in the same way.

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Which of the following Node.js modules would you typically use to handle file uploads?

fs
http
url
multer

In Node.js, to handle file uploads, you would typically use the multer module. multer is a middleware for handling multipart/form-data, which is the format used for file uploads. The other options (fs, http, and url) are commonly used for different purposes, such as working with files, creating HTTP servers, and parsing URLs, respectively.

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When using ES6+ modules, the import statement must be at the ________ of the file.

bottom
middle
top
end

When using ES6+ modules, the import statement must be at the top of the file. This is because ES6+ modules have a strict structure, and imports are processed before the module's code is executed. Placing the import statement at the top ensures that the imported dependencies are available throughout the module.

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Which of the following is required to serve static files in an Express application?

express.static()
app.static()
serveStatic()
staticFiles()

In Express.js, the express.static() middleware is used to serve static files like HTML, CSS, and JavaScript files. This middleware is essential to handle static assets in an Express application. The other options are not valid methods for serving static files.

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What is the primary purpose of using ESLint in a JavaScript project?

Ensure code quality and enforce coding style
Execute JavaScript code
Debug JavaScript code
Optimize JavaScript code

ESLint is primarily used to ensure code quality and enforce coding style standards in a JavaScript project. It helps identify and fix coding style issues, potential bugs, and maintainability problems in your codebase.

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