Difference Between Undefined and Null Mockest | JavaScript

11.

How does the typeof operator behave when applied to an "Undefined" value?

A). It returns "undefined". B). It returns "null". C). It throws an error. D). It returns "object".

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12.

Which of the following is an example of using "Null" in JavaScript?

A). let user = null; B). let user = undefined; C). let user; D). let user = '';

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13.

What does the expression typeof null return in JavaScript?

A). null B). object C). undefined D). function

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14.

Which statement best describes the relationship between "Undefined" and "Null" in JavaScript?

A). Undefined and Null are interchangeable and can be used interchangeably in code. B). Undefined and Null are distinct values representing different states in JavaScript. C). Undefined is a subset of Null, encompassing all possible values of Null. D). Null is a subset of Undefined, encompassing all possible values of Undefined.

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15.

What happens when a function does not explicitly return a value in JavaScript?

A). It returns "null". B). It returns "undefined". C). It throws an error. D). It returns "object".

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16.

How do you check if a variable has an "Undefined" value in JavaScript?

A). Using the undefined keyword. B). Using the null keyword. C). Using the typeof operator. D). Using the empty keyword.

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17.

Which of the following scenarios is a common cause of variables having an "Undefined" value?

A). When variables are explicitly set to "Undefined". B). When variables are declared but not initialized. C). When variables are intentionally set to "Null". D). When variables are assigned default values.

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18.

What does the expression null == undefined return in JavaScript?

A). 1 B). 0 C). undefined D). null

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19.

Which of the following statements is true regarding the behavior of "Undefined" and "Null" in JavaScript?

A). Undefined and Null are both falsy values in JavaScript. B). Undefined and Null are both truthy values in JavaScript. C). Undefined and Null have the same data type in JavaScript. D). Undefined and Null cannot be compared in JavaScript.

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20.

What is the purpose of using "Null" over "Undefined" in certain programming scenarios?

A). To represent an intentional absence of value or object reference. B). To assign default values to variables. C). To represent uninitialized variables. D). To check for variable existence.

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Difference Between Undefined and Null Mocktest

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