JavaScript Variables Mockest | JavaScript

11.

Which of the following will cause an error?

A). let a = 10; a = 20; B). const a = 10; a = 20; C). var a = 10; a = 20; D). None of the above

12.

What will be the output of the following code?

let a = 1; let b = 2; let c = a + b; console.log(c);

A). 12 B). 12 C). 3 D). NaN

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13.

Which statement is true about variables in JavaScript?

A). They must be declared before use B). They can only hold numbers C). They are statically typed D). They are strongly typed

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14.

What will be the output of the following code?

var a = 1; { var a = 2; } console.log(a);

A). 1 B). 2 C). undefined D). ReferenceError

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15.

Which of the following is correct about variable scope in JavaScript?

A). var is block-scoped B). let is function-scoped C). const is block-scoped D). All variables are global

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16.

What is the difference between let and var?

A). let is function-scoped, var is block-scoped B). let is block-scoped, var is function-scoped C). Both are block-scoped D). Both are function-scoped

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17.

What will be the output of the following code?

const a = 10; a = 20; console.log(a);

A). 10 B). 20 C). Error D). undefined

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18.

Can you reassign a value to a variable declared with let?

A). Yes B). No C). Only in strict mode D). Only inside a block

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19.

What will be the output of the following code?

console.log(a); var a = 10;

A). 10 B). undefined C). Error D). null

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20.

Which of the following is true about variable naming conventions in JavaScript?

A). Variable names can start with a number B). Variable names are case-insensitive C). Variable names can include spaces D). Variable names are case-sensitive

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