Reverse mapping in numeric enums in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a numeric enum named Direction.

Typescript

enum Direction {
  Up = [1],
  Down,
  Left,
  Right
}

Drag options to blanks, or click blank then click option'

A0

B1

C10

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning 1 to the first member, which changes the default numbering.

Leaving the first member unassigned but expecting it to start at 1.

The first enum member defaults to 0 if not assigned. Here, we explicitly assign 0 to Up.

2fill in blank

medium

Complete the code to get the name of the enum member with value 2.

Typescript

let directionName = Direction[[1]];

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A"Up"

B"Left"

C2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using the string name instead of the numeric value for reverse mapping.

Using a value not defined in the enum.

Numeric enums support reverse mapping. Using the numeric value 2 returns the member name 'Left'.

3fill in blank

hard

Fix the error in accessing the enum member name by value.

Typescript

console.log(Direction[[1]]);

Drag options to blanks, or click blank then click option'

A4

B1

C"Right"

D"Down"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a numeric value for reverse mapping.

Using a numeric value not assigned to any enum member.

Direction[1] returns 'Down' because Down is the second member with value 1.

4fill in blank

hard

Fill both blanks to create a reverse mapping lookup for the enum member with value 3.

Typescript

const value = [1];
const name = Direction[[2]];

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A3

B2

Cvalue

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong numeric value that does not correspond to any member.

Using a literal number instead of the variable in the second blank.

Assign 3 to value, then use Direction[value] to get the member name 'Right'.

5fill in blank

hard

Fill all three blanks to declare a numeric enum with custom start, then get the name of the member with value 101.

Typescript

enum Status {
  Active = [1],
  Inactive,
  Pending
}

const code = [2];
const statusName = Status[[3]];

Drag options to blanks, or click blank then click option'

A100

B101

Ccode

D102

Attempts:

3 left

💡 Hint

Common Mistakes

Starting enum at 0 instead of 100.

Using the numeric value directly instead of the variable in the last blank.

Start enum at 100, so Inactive is 101. Assign 101 to code, then use Status[code] to get 'Inactive'.