Enum members

Learn enum member access and reverse mapping.

Accessing enum members

You access enum members with dot notation: EnumName.Member. In a numeric enum, this access returns the member's number value. The value is the explicitly assigned number or, otherwise, the auto-incremented number.

enum Yon { Kuzey, Guney }
console.log(Yon.Kuzey);  // 0
console.log(Yon.Guney);  // 1

If a previous member was assigned a value, the next member automatically gets one more.

Reverse mapping

Numeric enums have reverse mapping: you can go from a number to the member name. A usage like Kod[10] returns the name of the member with that value as a string. This feature works only for numeric enums, not for string enums.

enum Kod { A = 10, B }
console.log(Kod[10]);  // "A"
console.log(Kod.B);   // 11

Reverse mapping lets you convert a number back to a name.

Exercise Reverse mapping in a color constant

Define a const named Renk mapping Kirmizi to 0 and Mavi to 1. Add reverse mapping by using number values as keys (e.g. key 1 maps to "Mavi"). Print the name obtained via Renk[1] with console.log.

Show example solution

const Renk = { Kirmizi: 0, Mavi: 1, 0: "Kirmizi", 1: "Mavi" };
console.log(Renk[1]);

Test yourself

In <code>enum Kod { A = 10, B }</code>, what is <code>Kod.B</code>?
- 1
- 11
- 10
- 0
Show answer

11 — Since <code>A = 10</code>, <code>B</code> automatically gets one more, that is <code>11</code>.

Find the name via reverse mapping

enum Kod { A = 10, B }
let isim = Kod[____];

Show answer

enum Kod { A = 10, B }
let isim = Kod[10];

Access and reverse mapping

Yon.Kuzey

Returns the member's number value
Kod[10]

Returns the name via reverse mapping
Reverse mapping

Works only for numeric enums
String enum

Does not support reverse mapping

Next lesson: Summary - Enum

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