Javascript Interview Questions For 2 Years Experience
Essential JavaScript Interview Questions for Candidates with 2 Years of Experience
As a candidate with 2 years of experience in Javascript, you may encounter some common interview questions. These generally include questions on your knowledge and understanding of core Javascript concepts such as data types, scope, closures, and object-oriented programming. Interviewers may also ask about your experience with various Javascript frameworks and libraries such as React, Angular, or jQuery. Additionally, expect questions on your ability to handle common challenges in Javascript programming, such as debugging, optimizing code, and dealing with browser compatibility issues. It is also important to have a good understanding of front-end development concepts such as HTML and CSS, as they are closely intertwined with Javascript. Showing enthusiasm for learning and staying updated with the constantly evolving Javascript ecosystem can also make a positive impression on the interviewer.
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1 - What is the difference between null and undefined?
Null represents an intentional absence of a value, whereas undefined means that a variable has been declared but has not been assigned a value.
2) Can you explain the concept of hoisting?
Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope. This means that regardless of where the variables and functions are declared in the code, they are treated as if they have been declared at the top.
3) What is closure and how is it used?
A closure is a function that has access to its parent scope, even after the parent function has closed. It is used to encapsulate data and functionality, allowing them to remain private and protected from external manipulation.
4) What is a callback function?
A callback function is a function that is passed as an argument to another function and is executed within that function. This allows for asynchronous programming and helps in avoiding callback hell.
5) What is scope in JavaScript?
Scope refers to the visibility of variables and functions within a particular portion of a code. Variables declared outside of a function have global scope, while those declared inside a function have local scope.
6) How do you handle errors in JavaScript?
Errors can be handled by using try catch blocks, where the code that is prone to errors is placed in the try block and any potential errors are caught and handled in the catch block.
7) What is the difference between == and ===?
The equal (==) operator compares values after converting their types, while the equal value and equal type (===) operator compares values without converting their types. Therefore, === will return true only if the operands are of the same type.
8) What is a prototype in JavaScript?
Every object in JavaScript has a prototype, which is an object from which it inherits properties and methods. Prototypes allow for properties and methods to be shared among objects.
9) What is the purpose of the ‘this’ keyword in JavaScript?
The ‘this’ keyword refers to the current object and is used to access its properties and methods within a function. Its value depends on how a function is called and is determined at runtime.
10) What is a closure in JavaScript?
A closure is a function that has access to its outer scope, even after the outer function has returned. This allows for private variables and methods to be created and used within the closure.
11) What is event bubbling and how can it be prevented?
Event bubbling is a pattern in which an event is handled by its parent elements in the DOM, even if it has been handled by its child elements. It can be prevented by using event.stopPropagation() in the event handling function.
12) How can you improve the performance of your code in JavaScript?
Some ways to improve performance in JavaScript include optimizing loops, minimizing DOM manipulation, using event delegation, and implementing proper caching techniques.
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13) What is a promise?
A promise is an object that represents the eventual completion or failure of an asynchronous operation. It allows for easier handling of asynchronous tasks and avoids callback hell.
14) What are the different data types in JavaScript?
JavaScript has six primitive data types: string, number, boolean, null, undefined, and symbol. It also has one complex data type: object.
15) How can you check if a variable is an array in JavaScript?
The Array.isArray() method can be used to check if a variable is an array in JavaScript. It returns a boolean value based on whether the variable is an array or not.
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