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https://github.com/nabin-8/javascript-interview


https://github.com/nabin-8/javascript-interview

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# Top 100 JS Interview Questions



1. Basics & Fundamentals --20

1. Variables & Datatypes --6

1. Operators & Conditions --8

1. Arrays --13

1. Loops --8

1. Functions --14

1. Strings --6

1. DOM --11

1. Error Handling --6

1. Objects -- 13

1. Events --10



### 1.Basics & Fundamentals - 20

1. What is JavaScript? What is the role of JavaScript engine?

1. What are client side and server side?

1. What are variables? What is the difference between var, let, and const? `V. IMP.`

1. What are some important string operations in JS?

1. What is DOM? What is the difference between HTML and DOM?

1. What are selectors in JS? `V. IMP.`

1. What is the difference between getElementByld,getElementsByClassName and getElementsByTagName?

1. What are data types in JS?

1. What are operators? What are the types of operators in JS?

1. What are the types of conditions statements in JS?

1. What is a loop? What are the types of loops in JS?

1. What are Functions in JS? What are the types of function?

1. What are Arrow Functions in JS? What is it use? `V.IMP.`

1. What are Arrays in JS? How to get, add & remove elements from arrays?

1. What are Objects in JS?

1. What is Scope in JavaScript? `V.IMP.`

1. What is Hoisting in JavaScript? `V.IMP.`

1. What is Error Handling in JS?

1. What is JSON?

1. What is asynchronous programming in JS? What is its use?



### 2.Variables & Datatypes -6

1. What are variables? What is the difference between var, let, and const ? `basics`

1. What are data types in JS? `basics`

1. What is the difference between primitive and non-primitive data types?

1. What is the difference between null and undefined in JS?

1. What is the use of typeof operator?

1. What is type coercion in JS? `V.IMP.`



### 3.Operators & Conditions - 8

1. What are operators? What are the types of operators in JS? `basics`

1. What is the difference between unary, binary, and ternary operators?

1. What is short-circuit evaluation in JS?

1. What is operator precedence?

1. What are the types of conditions statements in JS? `basics`

1. When to use which type of conditions statements in real applications?

1. What is the difference between == and ===? v. `V.IMP.`

1. What is the difference between Spread and Rest operator in JS?



### 4.Arrays - 13

1. What are Arrays in JS? How to get, add & remove elements from arrays? `basics`

1. What is the indexOf() method of an Array?

1. What is the difference between find() and filter() methods of an Array? `V.IMP.`

1. What is the slice() method of an Array?

1. What is the difference between push() and concat() methods of an Array?

1. What is the difference between pop() and shift() methods of an Array?

1. What is the splice() method of an Array?

1. What is the difference between the slice() and splice() methods?

1. What is the difference map() and forEach() array methods? `V. IMP.`

1. How to sort and reverse an array?

1. What is Array Destructuring in JS? `V.IMP.`

1. What are array-like objects In Js?

1. How to convert an array-like object into an array?



### 5.Loops - 8

1. What is a loop? What are the types of loops in JS? `basics`

1. What is the difference between while and for loops?

1. What is the difference between while and do-while loops? `V. IMP.`

1. What is the difference between break and continue statement? `V.IMP.`

1. What is the difference between for and for...of loop in JS?

1. What is the difference between for...of and for...in loop?

1. What is forEach method? Compare it with for...of and for...in loop?

1. When to use for...of loop and when to use foreach method in

applications?



### 6.Functions - 14

1. What are Functions in JS? What are the types of function? `basics`

1. What is the difference between named and anonymous functions?

1. What is function expression in JS?

1. What are Arrow Functions in JS? What is it use? `basics`

1. What are Callback Functions? What is it use? `V. IMP.`

1. What is Higher-order function In JS?

1. What is the difference between arguments and parameters?

1. In how many ways can you pass arguments to a function?

1. How do you use default parameters in a function?

1. What is the use of event handling in JS?

1. What are First-Class functions in JS?

1. What are Pure and Impure functions in JS? `V.IMP.`

1. What is Function Currying in JS?

1. What are call, apply, and bind method in JS? `V.IMP.`



### 7.Strings - 6

1. What is a String?

1. What are template literals and string interpolation in strings? `V-IMP.`

1. What is the difference between single quotes (''), double quotes ("") & backticks (``)?

1. What are some important string operations in JS? `basics`

1. What is string immutability? `V.IMP.`

1. In how many ways you can concatenate strings?



### 8.DOM-11

1. What is DOM? What is the difference between HTML and DOM? `basics`

1. How do you select, modify, create and remove DOM elements? `v.imp.`

1. What are selectors in JS? `basics`

1. Difference between getElementByld, getElementsByClassName and getElementsByTagName?

1. What is the difference between querySelector() and querySelectorAll()? `V-IMP.`

1. What are the methods to modify elements properties and attributes?

1. What is the difference between innerHTML and textContent? `V-IMP.`

1. How to add and remove properties of HTML elements?

1. How to add and remove style from HTML elements?

1. How to create new elements in DOM using JS?

1. Difference between createElement() and createTextNode()?



### 9.Error Handling

1. What is Error Handling in JS? `basics`

1. What is the role of finally block in JS?

1. What is the purpose of the throw statement in JS?` V.IMP.`

1. What is Error propagation in JS?

1. What are the best practices for error handling?

1. What are the different types of errors In JS?



### 10.Objects - 13

1. What are Objects in JS? `basics`

1. In how many ways we can create an object? `V.IMP.`

1. What is the difference between array and objects?

1. How do you add or modify or delete properties of an object?

1. Explain the difference between dot notation and bracket notation?

1. What are some common methods to iterate over the properties of an object?

1. How do you check if a property exists in an object?

1. How do you clone or copy an object?

1. What is the difference between deep copy and shallow copy in JS?

1. What is Set Object in JS? `V.IMP.`

1. What is Map Object in JS? `V.IMP.`



### 11.Events -10

1. What are Events? How are events triggered?

1. What are the types of events in JS?

1. What is Event Object in JS?

1. What is Event Delegation in JS? `V. IMP.`

1. What is Event Bubbling In JS? `V.ImP.`

1. How can you stop event propagation or event bubbling in JS?

1. What is Event Capturing in JS?

1. What is the purpose of the event.preventDefault() method in JS?

1. What is the use of "this" keyword in the context of event handling

1. How to remove an event handler from an element in JS?