Showing Topics for "javascript interview questions"

What are the types of errors in javascript?

Filed under: JavaScript Interview Questions

There are two types of errors in javascript.Syntax error: Syntax errors are mistakes or spelling problems in the code that cause the program to not execute at all or to stop running halfway through. Error messages are usually supplied as well.Logical error: Reasoning mistakes occur when the syntax i  ......

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What is DOM?

Filed under: JavaScript Interview Questions

DOM stands for Document Object Model.  DOM is a programming interface for HTML and XML documents.When the browser tries to render an HTML document, it creates an object based on the HTML document called DOM. Using this DOM, we can manipulate or change various elements inside the HTML document.

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Which method is used to retrieve a character from a certain index?

Filed under: JavaScript Interview Questions

The charAt() function of the JavaScript string finds a char element at the supplied index. The index number begins at 0 and continues up to n-1, Here n is the string length. The index value must be positive, higher than, or the same as the string length.

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What do you mean by BOM in Javascript?

Filed under: JavaScript Interview Questions

Browser Object Model is known as BOM. It allows users to interact with the browser. A browser's initial object is a window. As a result, you may call all of the window's functions directly or by referencing the window. The document, history, screen, navigator, location, and other attributes are avai

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What do mean by prototype design pattern?

Filed under: JavaScript Interview Questions

The Prototype Pattern produces different objects, but instead of returning uninitialized objects, it produces objects that have values replicated from a template – or sample – object. Also known as the Properties pattern, the Prototype pattern is used to create prototypes.The introduction of bus  ......

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Methods to create an object in javascript

Filed under: JavaScript Interview Questions

In JavaScript, there are several ways to declare or construct an object.Object.using Class.create Method.Object Literals.using Function.Object Constructor.

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Explain WeakSet in javascript

Filed under: JavaScript Interview Questions

In javascript, a Set is a collection of unique and ordered elements. Just like Set, WeakSet is also a collection of unique and ordered elements with some key differences:Weakset contains only objects and no other type.An object inside the weakset is referenced weakly. This means, that if the object   ......

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Why do we use callbacks in Javascript?

Filed under: JavaScript Interview Questions

A callback function is a method that is sent as an input to another function (now let us name this other function "thisFunction"), and it is performed inside the thisFunction after the function has completed execution.JavaScript is a scripting language that is based on events. Instead of waiting for  ......

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Difference between prototypal and classical inheritance in Javascript

Filed under: JavaScript Interview Questions

Programers build objects, which are representations of real-time entities, in traditional OO programming. Classes and objects are the two sorts of abstractions. A class is a generalization of an object, whereas an object is an abstraction of an actual thing. A Vehicle, for example, is a specializati  ......

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What are the primitive data types in JavaScript?

Filed under: JavaScript Interview Questions

A primitive is a data type that isn't composed of other data types. It's only capable of displaying one value at a time. By definition, every primitive is a built-in data type (the compiler must be knowledgeable of them) nevertheless, not all built-in datasets are primitives. In JavaScript, there ar  ......

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Is JavaScript a pass-by-reference or pass-by-value language?

Filed under: JavaScript Interview Questions

The variable's data is always a reference for objects, hence it's always pass by value. As a result, if you supply an object and alter its members inside the method, the changes continue outside of it. It appears to be pass by reference in this case. However, if you modify the values of the object v

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Write the code for dynamically inserting new components

Filed under: JavaScript Interview Questions

With javascript you can insert content in your html document. This is the most popular feature of javascript programming. Here is the example of how you can insert element in your html document.<html> 
<head> 
<title>inserting new components dynamically</title&g  ......

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Write the code to find the vowels

Filed under: JavaScript Interview Questions

const findVowels = str => {
  let count = 0
  const vowels = ['a', 'e', 'i', 'o', 'u']
  for(let char of str.toLowerCase()) {
    if(vowels.includes(char)) {
      count++
    }
  }
  return count
}

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What do you mean by strict mode in javascript and characteristics of javascript strict-mode?

Filed under: JavaScript Interview Questions

In ECMAScript 5, a new feature called JavaScript Strict Mode allows you to write a code or a function in a "strict" operational environment. In most cases, this language is 'not particularly severe' when it comes to throwing errors. In 'Strict mode,' however, all forms of errors, including silent er  ......

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What is NaN property in JavaScript?

Filed under: JavaScript Interview Questions

NaN property represents the “Not-a-Number” value. It indicates a value that is not a legal number.typeof of NaN will return a Number.To check if a value is NaN, we use the isNaN() function,Note- isNaN() function converts the given value to a Number type, and then equates to NaN.isNaN("Hello") &n  ......

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Is javascript a statically typed or a dynamically typed language?

Filed under: JavaScript Interview Questions

JavaScript is a dynamically typed language. In a dynamically typed language, the type of a variable is checked during run-time in contrast to a statically typed language, where the type of a variable is checked during compile-time.Since javascript is a loosely(dynamically) typed language, variables   ......

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Difference between var and let keyword in javascript

Filed under: JavaScript Interview Questions

Some differences are From the very beginning, the 'var' keyword was used in JavaScript programming whereas the keyword 'let' was just added in 2015.The keyword 'Var' has function scope. Anywhere in the function, the variable specified using var is accessible but in ‘let’ the scope of a vari  ......

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Difference between “ == “ and “ === “ operators

Filed under: JavaScript Interview Questions

Both are comparison operators. The difference between both the operators is that “==” is used to compare values whereas, “ === “ is used to compare both values and types.var x = 2;
var y = "2";
(x == y)  // Returns true since the value of both x and y is the same
(x === y) // Returns

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Why do we use the word “debugger” in javascript?

Filed under: JavaScript Interview Questions

The debugger for the browser must be activated in order to debug the code. Built-in debuggers may be switched on and off, requiring the user to report faults. The remaining section of the code should stop execution before moving on to the next line while debugging.Learn more javascript mcqs here.&nb

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Explain Hoisting in javascript

Filed under: JavaScript Interview Questions

Hoisting is the default behaviour of javascript where all the variable and function declarations are moved on top.This means that irrespective of where the variables and functions are declared, they are moved on top of the scope. The scope can be both local and global.Example 1:hoistedVariable = 3;
  ......

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Showing 20 Search Results for : javascript interview questions

What are the types of errors in javascript?

What is DOM?

Which method is used to retrieve a character from a certain index?

What do you mean by BOM in Javascript?

What do mean by prototype design pattern?

Methods to create an object in javascript

Explain WeakSet in javascript

Why do we use callbacks in Javascript?

Difference between prototypal and classical inheritance in Javascript

What are the primitive data types in JavaScript?

Is JavaScript a pass-by-reference or pass-by-value language?

Write the code for dynamically inserting new components

Write the code to find the vowels

What do you mean by strict mode in javascript and characteristics of javascript strict-mode?

What is NaN property in JavaScript?

Is javascript a statically typed or a dynamically typed language?

Difference between var and let keyword in javascript

Difference between “ == “ and “ === “ operators

Why do we use the word “debugger” in javascript?

Explain Hoisting in javascript

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