21.Which built-in method returns the character at the specified index?

charAt() method returns the character at the specified index.

22.Which built-in method combines the text of two strings and returns a new string?

concat() method returns the character at the specified index.

23.Which built-in method calls a function for each element in the array?

forEach() method calls a function for each element in the array.

24.Which built-in method returns the index within the calling String object of the first occurrence of the specified value?

indexOf() method returns the index within the calling String object of the first occurrence of the specified value, or − 1 if not found.

25.Which built-in method returns the length of the string?

length() method returns the length of the string.

26.Which built-in method removes the last element from an array and returns that element?

pop() method removes the last element from an array and returns that element.

27.Which built-in method adds one or more elements to the end of an array and returns the new length of the array?

push() method adds one or more elements to the end of an array and returns the new length of the array.

28.Which built-in method reverses the order of the elements of an array?

reverse() method reverses the order of the elements of an array − − the first becomes the last, and the last becomes the first.

29.Which built-in method sorts the elements of an array?

sort() method sorts the elements of an array.

30.Which built-in method returns the characters in a string beginning at the specified location?

substr() method returns the characters in a string beginning at the specified location through the specified number of characters.

31.Which built-in method returns the calling string value converted to lower case?

toLowerCase() method returns the calling string value converted to lower case.

32.Which built-in method returns the calling string value converted to upper case?

toUpperCase() method returns the calling string value converted to upper case.

33.Which built-in method returns the string representation of the number's value?

toString() method returns the string representation of the number's value.

34.What are the variable naming conventions in JavaScript?

While naming your variables in JavaScript keep following rules in mind.

You should not use any of the JavaScript reserved keyword as variable name. These keywords are mentioned in the next section. For example, break or boolean variable names are not valid.

JavaScript variable names should not start with a numeral (0-9). They must begin with a letter or the underscore character. For example, 123test is an invalid variable name but _123test is a valid one.

JavaScript variable names are case sensitive. For example, Name and name are two different variables.

35.How typeof operator works?

The typeof is a unary operator that is placed before its single operand, which can be of any type. Its value is a string indicating the data type of the operand.

The typeof operator evaluates to "number", "string", or "boolean" if its operand is a number, string, or boolean value and returns true or false based on the evaluation.

36.What typeof returns for a null value?

It returns "object".
Can you access Cookie using javascript?JavaScript can also manipulate cookies using the cookie property of the Document object. JavaScript can read, create, modify, and delete the cookie or cookies that apply to the current web page.

37.How to create a Cookie using JavaScript?

The simplest way to create a cookie is to assign a string value to the document.cookie object, which looks like this −
Syntax −

38.How to read a Cookie using JavaScript?

Reading a cookie is just as simple as writing one, because the value of the document.cookie object is the cookie. So you can use this string whenever you want to access the cookie.

The document.cookie string will keep a list of name = value pairs separated by semicolons, where name is the name of a cookie and value is its string value.

You can use strings' split() function to break the string into key and values.

39.How to delete a Cookie using JavaScript?

Sometimes you will want to delete a cookie so that subsequent attempts to read the cookie return nothing. To do this, you just need to set the expiration date to a time in the past.

40.How to redirect a url using JavaScript?

this is very simple to do a page redirect using JavaScript at client side. To redirect your site visitors to a new page, you just need to add a line in your head section as follows −