Javascript Interview Questions For 1 Year Experience

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Javascript Interview Questions For 1 Year Experience

Top Interview Questions for JavaScript Candidates with 1 Year of Experience

The Javascript Interview Questions for 1 year experience typically cover a wide range of topics related to the candidate's proficiency and understanding of Javascript. These may include questions about the core concepts of Javascript, such as variables, loops, functions, and objects, as well as its advanced features like closures, prototypal inheritance, and event handling. Interviewers may also ask about the candidate's experience with popular Javascript libraries and frameworks, such as jQuery, AngularJS, and React. Additionally, questions may be asked about the candidate's experience working with different data formats, such as JSON and XML, and their understanding of DOM manipulation. Overall, the purpose of these questions is to assess the candidate's practical knowledge and problem-solving skills in using Javascript to create dynamic and interactive web applications.

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1 - What is closure in JavaScript?

Answer: A closure is a function that has access to variables defined outside its scope. It is created when an inner function is returned from an outer function that has already been executed. This allows the inner function to access variables and parameters from its parent function, even after the parent function has finished executing.

2) What is the difference between var, let and const?

Answer: Var declarations are globally scoped or function scoped, while let and const are block scoped. Var variables can be redeclared and updated, while let variables can be updated but not redeclared, and const variables can neither be updated nor redeclared. Const variables must be assigned a value when declared.

3) What is hoisting in JavaScript?

Answer: Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope before code execution. However, only the variable declarations are hoisted, not the actual assignment or function definitions.

4) What is the use of strict mode in JavaScript?

Answer: Strict mode is a way to opt in to a newer, stricter version of JavaScript, where certain actions are prohibited and certain errors are thrown. It helps to avoid common pitfalls and enables better error handling in your code.

5) What is the difference between == and === in JavaScript?

Answer: The double equals (==) operator compares only the values of two variables, converting them to the same type if needed, while the triple equals (===) operator also checks for the equality of types.

6) What is event bubbling and event propagation in JavaScript?

Answer: Event bubbling is the default behavior where an event triggers on the deepest element and then moves up the DOM tree. Event propagation is the opposite, where the event is triggered on the parent elements first and then moves down the DOM tree.

7) How do you check the type of a variable in JavaScript?

Answer: The typeof operator can be used to check the type of a variable. It returns a string indicating the type of the variable, such as “number,” “string,” “object,” etc.

8) What is the difference between null and undefined in JavaScript?

Answer: Null represents an intentional absence of value, while undefined represents a variable that has been declared but not assigned a value. In other words, null is a value that has been explicitly set, while undefined means the value has not been set.

9) What is a JavaScript event loop?

Answer: The event loop is a programming construct that continuously listens for events and executes the appropriate code when an event is detected. It ensures that JavaScript code runs only one piece at a time, avoiding any blocking or delays.

10) How do you handle errors in JavaScript?

Answer: Errors can be handled in JavaScript using try/catch/finally blocks. The try block contains the code that may throw an error, the catch block handles the error if it occurs, and the finally block allows you to execute code regardless of whether an error occurred or not.

11) What is a Promise in JavaScript?

Answer: A Promise is a special JavaScript object that represents the result of an asynchronous operation. It can be in one of three states: pending (initial state), fulfilled (operation completed successfully), or rejected (operation failed).

12) How do you limit the scope of a variable in JavaScript?

Answer: You can use the IIFE (Immediately Invoked Function Expression) pattern, where the variable is declared and initialized inside a function that is immediately invoked, creating a private scope for the variable.

13) How does JavaScript handle asynchronous code?

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Answer: JavaScript uses the event loop and callback functions to handle asynchronous code. Callback functions are created that will be executed once the asynchronous task is completed. This allows the event loop to continue to execute other tasks while waiting for the asynchronous task to finish.

14) How do you compare two objects in JavaScript?

Answer: Unlike primitive data types, objects cannot be compared with the == or === operators because they are compared by reference and not by value. However, you compare the properties and values of two objects using the JSON.stringify() method or by manually looping through the properties and comparing them.

15) What is a pure function in JavaScript?

Answer: A pure function is a function that always returns the same result for the same input, and it does not cause side effects, such as modifying variables or objects outside its scope. Pure functions are easy to test and help to prevent bugs and unexpected behavior in your code.

 

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