How do I get enum key strings?
To get an enum key by value:
- Use the Object. values() method to get an array of the enum’s values.
- Use the indexOf() method to get the index of the value in the array.
- Use the Object. keys() method to get an array of the enum’s keys.
- Access the array of keys at the specific index.
What is enum TypeScript?
In TypeScript, enums, or enumerated types, are data structures of constant length that hold a set of constant values. Each of these constant values is known as a member of the enum. Enums are useful when setting properties or values that can only be a certain number of possible values.
Can I use enum as a type in TypeScript?
Enums or enumerations are a new data type supported in TypeScript. Most object-oriented languages like Java and C# use enums. This is now available in TypeScript too. In simple words, enums allow us to declare a set of named constants i.e. a collection of related values that can be numeric or string values.
How do you find the value of an enum?
To get the value of enum we can simply typecast it to its type. In the first example, the default type is int so we have to typecast it to int. Also, we can get the string value of that enum by using the ToString() method as below.
How do I convert a string to enum in TypeScript?
To convert a string to an enum: Use keyof typeof to cast the string to the type of the enum. Use bracket notation to access the corresponding value of the string in the enum.
Can you loop through an enum in TypeScript?
Iterating over the keys
Of course, it’s also possible to loop over the keys of a string enum, using Object. keys().
What is the difference between enum and string?
If your set of parameters is limited and known at compile time, use enum . If your set of parameters is open and unkown at compile time, use strings.
How do you use enums?
You should always use enums when a variable (especially a method parameter) can only take one out of a small set of possible values. Examples would be things like type constants (contract status: “permanent”, “temp”, “apprentice”), or flags (“execute now”, “defer execution”).
Is an enum an object TypeScript?
Enumerations (or enums) are a supported data type in TypeScript. Enums are used in most object-oriented programming languages like Java and C# and are now available in TypeScript too. They are one of the few features of TypeScript which isn’t a type-level extension of JavaScript.
What does enum valueOf return?
valueOf. Returns the enum constant of the specified enum type with the specified name. The name must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
How do you validate enum values in TypeScript?
To check if a value exists in an enum:
- Use the Object. values() method to get an array of the enum’s values.
- Use the includes() method to check if the value exists in the array.
- The includes method will return true if the value is contained in the enum and false otherwise.
Can you map through an enum?
In other words to use the map() method with an enum, we have to convert the enum keys or values to an array and call the map() method on the result. If you want to map over the values of an enum directly, you can get an array of an enum’s values in the following ways. Copied!
How do I create a map in TypeScript?
Creating a Map
Use Map type and new keyword to create a map in TypeScript. let myMap = new Map<string, number>(); To create a Map with initial key-value pairs, pass the key-value pairs as an array to the Map constructor.
Which is better enum or string?
Enums limit you to the required set of inputs whereas even if you use constant strings you still can use other String not part of your logic. This helps you to not make a mistake, to enter something out of the domain, while entering data and also improves the program readability.
Why do we need enum?
Enums are lists of constants. When you need a predefined list of values which do represent some kind of numeric or textual data, you should use an enum. You should always use enums when a variable (especially a method parameter) can only take one out of a small set of possible values.
Why enums are better than constants?
Why do we use enum?
You should use enum types any time you need to represent a fixed set of constants. That includes natural enum types such as the planets in our solar system and data sets where you know all possible values at compile time—for example, the choices on a menu, command line flags, and so on.
Can enum values be objects?
An enum is a data type that can be created by a Java programmer to represent a small collection of possible values. Technically, an enum is a class and its possible values are objects.
What does enum name return?
The java.lang.Enum.name() method returns the name of this enum constant, exactly as declared in its enum declaration.
Can enum have multiple values?
The Enum constructor can accept multiple values.
Can we use enum as map key?
Using Enum as key makes it possible to do some extra performance optimization, like a quicker hash computation since all possible keys are known in advance.
How do you define an enum map?
EnumMap is an ordered collection and they are maintained in the natural order of their keys(the natural order of keys means the order on which enum constants are declared inside enum type ) It’s a high-performance map implementation, much faster than HashMap.
Does TypeScript have a map type?
TypeScript map is a new data structure added in ES6 version of JavaScript. It allows us to store data in a key-value pair and remembers the original insertion order of the keys similar to other programming languages. In TypeScript map, we can use any value either as a key or as a value.
Can we use map in TypeScript?
TypeScript does support Maps “natively” now, so it simply allows ES6 Maps to be used when the output is ES6.
What can I use instead of enum?
Alternatives to enums in TypeScript
- Unions of singleton values. Unions of string literal types.
- Discriminated unions. Step 1: the syntax tree as a class hierarchy.
- Object literals as enums. Object literals with string-valued properties.
- Enum pattern.
- Summary of enums and enum alternatives.
- Acknowledgement.
- Further reading.