Introduction
If you are looking for advanced level JavaScript interview questions to prepare for your next interview, we have curated the most frequently asked in interviews. After you have gone through the JavaScript tutorial and revised the basic JavaScript concepts, look at these advanced JavaScript questions and answers.
JavaScript Interview Questions for Experienced Developers
1. What is the ‘Strict’ mode in JavaScript and how can it be enabled?
Strict mode is a feature in JavaScript that was introduced in ECMAScript 5. When enabled, it enforces additional constraints on your code, making it follow stricter rules. This feature prevents certain actions from being taken and throws more exceptions. To enable strict mode, you need to add the following expression at the beginning of your script or function:
"use strict";2. How to get the status of a CheckBox?
To set or return the checked status of a checkbox field, you can use the DOM Input Checkbox Property. It can also be used to reflect the HTML Checked attribute.
document.getElementById("GFG").checked; The CheckBox returns True if it is checked.
3. How to explain closures in JavaScript and when to use it?
A closure is a feature in JavaScript where an inner function has access to the outer (enclosing) function’s variables. This includes the outer function’s variables, parameters, and even the variables from the global scope.
// Explanation of closure
function foo() {
let b = 1;
function inner() {
return b;
}
return inner;
}
let get_func_inner = foo();
console.log(get_func_inner());
console.log(get_func_inner());
console.log(get_func_inner());Closures can be used in the following cases:
- Data Privacy: To create private variables.
- Function Factories: To generate functions dynamically.
- Event Handlers: To maintain state between function calls.
4. What is the difference between call() and apply() methods?
Both call() and apply() are used to invoke functions and set this inside the function.
- call(): Invokes the function with the specified this value and arguments provided individually.
- apply(): Invokes the function with the specified this value and arguments provided as an array.
Must Read: JAVASCRIPT INTERVIEW QUESTIONS FOR BEGINNERS
5. How to target a particular frame from a hyperlink in JavaScript?
You can use the target attribute in the hyperlink to target a particular frame from a hyperlink in JavaScript:
<a href="/OlibrBlogs.htm" target="newframe">New Page</a> 6. What are the errors shown in JavaScript?
Types of Errors in JavaScript
- Syntax Errors: Errors in the syntax of the code.
- Reference Errors: Accessing variables that don’t exist.
- Type Errors: Operations on incompatible types.
- Range Errors: Numbers out of range.
- Eval Errors: Errors related to the eval() function.
- URI Errors: Errors in URI handling functions.
7. What is the difference between JavaScript and Jscript?
- JavaScript: Developed by Netscape, it is the standard scripting language for web browsers. It is used to design client and server-side applications. It is completely independent of Java language.
- JScript: It is a scripting language by Microsoft. It is an implementation of the ECMAScript standard, used to design active online content for the World Wide Web.
8. What does the var myArray = [[]]; statement declare?
JavaScript Interview Questions for Experienced
Dive deep into JavaScript interview questions designed for experienced developers.
PublishedMay 29, 2024
CategoryExperienced Interview Questions
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