Difference Between Undefined and Null Mockest | JavaScript

1.

What is the difference between "Undefined" and "Null" in JavaScript?

A). Undefined is a value, while Null is an absence of value. B). Undefined is an absence of value, while Null is a value. C). Undefined is never intentional, while Null is always intentional. D). Undefined is always intentional, while Null is never intentional.

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2.

When does a variable typically have an "Undefined" value?

A). When it is intentionally set to represent no value. B). When it is assigned a default value. C). When it is declared but not initialized. D). When it is explicitly set to "Undefined".

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3.

How is "Null" different from "Undefined"?

A). Null represents variables that have been initialized but not declared. B). Null represents an intentional absence of value or object reference. C). Null is never used in programming. D). Null is a substitute for 'Undefined'.

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4.

Which statement is true regarding the use of "Undefined"?

A). Undefined is commonly used to reset variables in loops. B). Undefined is generally avoided and considered a programming error. C). Undefined is used to represent empty strings. D). Undefined is only used in function declarations.

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5.

When does the JavaScript engine assign an "Undefined" value to a variable?

A). When the variable is intentionally set to "Undefined". B). When the variable is not declared but used. C). When the variable is declared but not initialized. D). When the variable is initialized with the value "Undefined".

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6.

Which of the following correctly describes the purpose of "Null" in JavaScript?

A). Null is used to represent an empty array. B). Null is used to indicate that a variable is uninitialized. C). Null is used to represent an intentional absence of value. D). Null is used to check for object properties.

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7.

What is the result of the expression typeof undefinedVariable if undefinedVariable is not declared?

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

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8.

Which of the following is a valid use case for "Null" in JavaScript?

A). Storing default values in variables. B). Clearing or resetting object references. C). Assigning placeholders in arrays. D). Checking if a variable exists.

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9.

How do you assign a variable to have a value of "Null"?

A). Using the assignment operator =. B). Using the null keyword. C). Using the undefined keyword. D). Using the void operator.

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10.

Which of the following statements is correct regarding the comparison of "Undefined" and "Null"?

A). Undefined and Null are strictly equal in JavaScript. B). Undefined and Null are not strictly equal in JavaScript. C). Undefined is considered a subtype of Null. D). Null is considered a subtype of Undefined.

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