Mantra Technologies Content Lead Interview Questions and Answers

JS Prototype is a mechanism for inheritance and sharing properties among objects.

• Prototype is a property of every JavaScript function.

• It allows objects to inherit properties and methods from other objects.

• Modifying the prototype of a function affects all instances of that function.

• Prototype chain is used to look up properties and methods of an object.

• Prototype can be used to add new methods and properties to existing o

To find the total number without any loop in Node.js

• Use the reduce() method to sum up the values in an array

• Use the length property of an array to get the total number of elements

• Use the Object.keys() method to get the total number of keys in an object

Promises, async/await, and callbacks are all ways to handle asynchronous operations in Node.js.

• Callbacks are functions passed as arguments to another function and called when the operation is complete.

• Promises represent a value that may not be available yet, but will be resolved at some point in the future.

• Async/await is a syntax for writing asynchronous code that looks like synchronous code.

• Callbacks are the oldest an...read more

Promises are used in Node to handle asynchronous operations and avoid callback hell.

• Promises simplify error handling and make code more readable.

• Promises allow for chaining multiple asynchronous operations.

• Promises can be used with async/await to write synchronous-looking code.

• Example: fetching data from an API using axios library with promises.

• Example: reading a file with promises in Node's fs module.

Sequelize is an ORM for Node.js that supports multiple databases and provides easy data modeling and querying.

• Sequelize is used to interact with databases in Node.js

• It supports multiple databases like MySQL, PostgreSQL, SQLite, etc.

• It provides easy data modeling and querying with its object-relational mapping

• Example: const sequelize = new Sequelize('database', 'username', 'password', { dialect: 'mysql' });

Count the number of substrings in a given string that are divisible by 6.

• Iterate through all possible substrings of the given string.

• Check if the substring is a valid integer and not starting with 0.

• If the substring is divisible by 6, increment the count.

• Return the count of substrings that are divisible by 6.