TypeScript Reference : Decorators

Decorators in TypeScript are a powerful feature that allows you to add metadata to classes, methods, properties, and parameters at design time. They provide a way to modify the behavior of these elements without changing their original definition. Decorators are a form of metaprogramming and can be used to implement various cross-cutting concerns such as logging, validation, caching, and more.

In this complete guide, we will explore the different types of decorators available in TypeScript and how to use them effectively. We’ll start by understanding the basic syntax and usage of decorators, and then dive into more advanced topics such as decorator factories, class decorators, method decorators, property decorators, and parameter decorators.

We’ll also discuss some best practices for using decorators and explore some real-world examples to help you get a better understanding of how they can be used in practical scenarios. By the end of this guide, you’ll have a solid understanding of TypeScript decorators and be able to leverage their power to enhance your code and make it more maintainable and reusable.

If you’re serious about developing high-quality TypeScript applications, understanding and mastering decorators is essential. Decorators enable you to separate cross-cutting concerns from the core logic of your code, making it more modular and easier to maintain. So let’s dive in and explore the world of TypeScript decorators!

What are Decorators in TypeScript?

Decorators are a language feature in TypeScript that allow you to add behavior to existing classes, methods, properties, or other declarations. They are a way of modifying or enhancing the functionality of a declaration without modifying its code directly.

In TypeScript, decorators are declared using the ‘@’ symbol followed by the decorator name, which is then placed just before the declaration being decorated. Decorators can either be a function or a class that defines the behavior to be added to the declaration.

Why use Decorators?

Decorators have a wide range of uses and benefits in TypeScript. Some common use cases for decorators include:

• Modifying behavior: Decorators can be used to modify the behavior of a class, method, or property. This can include adding validation, logging, caching, or any other kind of behavior that needs to be added to the declaration.
• Code organization: Decorators can be used to organize code by separating concerns. Instead of adding all the logic and functionality to a single class, decorators allow you to split it into smaller, reusable decorators that can be applied to multiple declarations.
• Metadata and reflection: Decorators can also be used to add metadata to a declaration, which can then be used at runtime for reflection or other purposes. This can be useful for frameworks or libraries that need additional information about a declaration.

How do Decorators work?

When a decorator is applied to a declaration, it is executed at runtime and has the opportunity to modify or enhance the behavior of the declaration. The decorator function or class takes the declaration as its input and returns a new declaration with the desired behavior added.

Decorators can be applied to classes, methods, properties, parameters, and other declarations. They are applied using the ‘@’ symbol followed by the decorator name just before the declaration being decorated. Multiple decorators can be applied to a single declaration, and they are executed in the order they are defined.

It’s important to note that decorators are an experimental feature in TypeScript and are subject to change. However, they are widely used in frameworks and libraries like Angular, where they provide powerful tools for extending and customizing the behavior of declarations.

How to Use Decorators in TypeScript

Decorators are a special kind of declaration that can be used to modify classes, methods, properties, parameters, and accessor declarations at design time. They provide a way to add annotations or metadata to these declarations, which can then be used by other code at runtime. TypeScript decorators are inspired by the decorator pattern from object-oriented design.

Defining a Decorator

To define a decorator, you simply write a function that can be called with a variety of different arguments. The function should return a new function that will be called with the same arguments as the original function:

function decorator(target: any, key: string) {

let value = target[key];
const getter = function() {
console.log(`Getting value: ${value}`);
return value;
};
const setter = function(newValue: any) {
console.log(`Setting value: ${newValue}`);
value = newValue;
};
delete target[key];
Object.defineProperty(target, key, {
get: getter,
set: setter
});
}
class Example {
@decorator
property: string = 'initial value';
}
const example = new Example();
console.log(example.property);    // Getting value: initial value
example.property = 'new value';   // Setting value: new value
console.log(example.property);    // Getting value: new value

Applying a Decorator

To apply a decorator to a declaration, you simply place the decorator above the declaration. The decorator is called with metadata about the declaration, such as the constructor function for a class or the prototype object for a method. You can also apply multiple decorators to a single declaration:

@firstDecorator

@secondDecorator
class Example {
@thirdDecorator
method() {}
}

Using Decorators

Decorators can be used to add additional functionality to classes, methods, properties, and more. For example, you could use a decorator to instrument a method for performance tracking, or to validate the input parameters for a method. Decorators can also be used to implement cross-cutting concerns such as logging or authorization.

Conclusion

Decorators are a powerful feature in TypeScript that allow you to add additional behavior or metadata to your declarations. They can be applied to classes, methods, properties, and more, and can be used to implement a wide range of functionality. By understanding how to define and apply decorators, you can take advantage of this powerful language feature.

Decorators for Classes in TypeScript

In TypeScript, decorators can also be applied to classes. Class decorators are applied to the constructor of the class and can be used to modify its behavior.

Syntax

The syntax for applying a decorator to a class is as follows:

@decorator

class MyClass {
// class body
}

Here, the @decorator is the decorator expression and it is applied to the class MyClass.

Class Decorator Example

Let’s take an example to understand how class decorators work in TypeScript. Suppose we have a decorator named log which logs a message before and after the class constructor executes:

function log(target: Function) {

console.log('Before constructor');
console.log('Class Name:', target.name);
console.log('After constructor');
}
@log
class MyClass {
constructor() {
console.log('Inside constructor');
}
}

In this example, when the MyClass is declared with the @log decorator, the log function is executed. The output of this code would be:

1. Before constructor
2. Class Name: MyClass
3. After constructor
4. Inside constructor

Multiple Decorators

A class can have multiple decorators applied to it. In such cases, the decorators are applied in the order they appear, from bottom to top.

For example, let’s say we have two decorators, decoratorA and decoratorB. When applied to the class, the decoratorB will be executed first, followed by decoratorA.

Summary

• Class decorators are applied to the constructor of the class.
• Class decorators can be used to modify the behavior of a class.
• A class can have multiple decorators applied to it.
• Decorators are applied in the order they appear, from bottom to top.

In conclusion, class decorators in TypeScript are a powerful feature that allows developers to modify the behavior of classes. By applying decorators to classes, developers can add additional functionality or modify existing functionality of a class.

Decorators for Properties in TypeScript

In TypeScript, decorators can also be applied to properties. This allows you to modify the behavior of specific properties within your class or interface.

Creating a Property Decorator

To create a property decorator, you need to define a function that takes three parameters:

1. The target: this is the constructor function of the class if the property is static, or the prototype of the class if the property is non-static.
2. The property key: this is the name of the property.
3. The property descriptor: this is an object that contains metadata about the property, such as its value, whether it is writable, configurable, etc.

Here is an example of a property decorator:

function required(target: any, propertyKey: string) {

// Modify the property descriptor
const descriptor = Object.getOwnPropertyDescriptor(target, propertyKey);
descriptor.writable = false;
// Re-define the property
Object.defineProperty(target, propertyKey, descriptor);
}
class Person {
@required
name: string;
constructor(name: string) {
this.name = name;
}
}
const person = new Person('John');
person.name = 'Jane'; // Throws an error since the property is read-only

Using the Property Decorator

In the example above, the @required decorator is used to make the name property read-only. When the required decorator is applied to the name property, it modifies the property descriptor to make it non-writable. This means that once the property is assigned a value, it cannot be changed.

Applying Multiple Property Decorators

Multiple decorators can be applied to a single property. When multiple decorators are applied, they are executed in the order they are defined, from bottom to top.

function minLength(length: number) {

return function (target: any, propertyKey: string) {
const descriptor = Object.getOwnPropertyDescriptor(target, propertyKey);
const originalSetter = descriptor.set;
descriptor.set = function (value: any) {
if (value.length < length)="">
throw new Error('Value is too short');
}
originalSetter.call(this, value);
};
Object.defineProperty(target, propertyKey, descriptor);
};
}
class Person {
@minLength(5)
name: string;
constructor(name: string) {
this.name = name;
}
}
const person = new Person('John');
person.name = 'Jane'; // Throws an error since the value is too short

In the example above, the minLength decorator is applied to the name property. This decorator checks if the length of the value being assigned to the property is less than the specified minimum length. If it is, it throws an error. If the value meets the length requirement, it calls the original property setter to assign the value.

Summary

In TypeScript, property decorators allow you to modify the behavior of specific properties within your classes or interfaces. They can be used to make properties read-only, validate values before assigning them, or add additional logic to property accessors.

Decorators for Methods in TypeScript

Methods in TypeScript can also be decorated using decorators. Decorators for methods can be used to modify the behavior of the method or to provide additional functionality.

1. Method Decorators

Method decorators are used to modify the behavior of a method. They can be applied to the method declaration using the @ symbol followed by the decorator name.

Example:

@decorator

class MyClass {
@decorator
myMethod() {
// method implementation
}
}

2. Decorator Factory for Methods

A decorator factory is a function that returns the actual decorator. It allows you to pass arguments to the decorator function.

Example:

function myDecoratorFactory(arg1: string, arg2: number) {

return function myDecorator(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
// decorator implementation
}
}
class MyClass {
@myDecoratorFactory('argument 1', 2)
myMethod() {
// method implementation
}
}

3. Decorators for Method Parameters

Decorators can also be applied to the parameters of a method. They receive three arguments: the target object, the method name, and the parameter index.

Example:

function myParameterDecorator(target: any, propertyKey: string, parameterIndex: number) {

// decorator implementation
}
class MyClass {
myMethod(@myParameterDecorator param1: string, @myParameterDecorator param2: number) {
// method implementation
}
}

4. Method Decorator Execution Order

When multiple decorators are applied to a method, they are executed in the following order:

1. Topmost decorator nearest to the method declaration
2. Next decorator in the chain towards the bottom

5. Using Multiple Decorators on a Method

Multiple decorators can be applied to a method by chaining them using the @ symbol.

Example:

function decorator1(target: any, propertyKey: string, descriptor: PropertyDescriptor) {

// decorator 1 implementation
}
function decorator2(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
// decorator 2 implementation
}
class MyClass {
@decorator1
@decorator2
myMethod() {
// method implementation
}
}

6. Decorators for Method Return Value

Decorators can also be applied to the return value of a method. They receive three arguments: the target object, the method name, and the method descriptor.

Example:

function myReturnValueDecorator(target: any, propertyKey: string, descriptor: PropertyDescriptor) {

// decorator implementation
}
class MyClass {
@myReturnValueDecorator
myMethod() {
// method implementation
}
}

7. Limitations of Method Decorators

There are few limitations to keep in mind when working with method decorators:

• Method decorators cannot be used in JavaScript because they are not part of the ECMAScript standard.
• Method decorators cannot be applied to static methods.
• Method decorators cannot be applied to accessors (getters/setters).

Decorators for Parameters in TypeScript

In TypeScript, you can also apply decorators to function parameters. Decorators for parameters have the following syntax:

@decorator
function functionName(@decorator parameter1: type, @decorator parameter2: type, ...) {
// Function body
}

You can apply multiple decorators to a single parameter, each decorator separated by a comma. The decorators are applied in the order in which they appear.

Example: Applying Decorators to Parameters

Let’s say we have a class called Person with a method called sayHello:

class Person {
name: string;
constructor(name: string) {
this.name = name;
}
sayHello(@logParameter message: string) {
console.log(`Hello, ${this.name}! ${message}`);
}
}

In the example above, we have applied a decorator called logParameter to the message parameter of the sayHello method. This decorator could be used to log the value of the parameter:

function logParameter(target: any, methodName: string, parameterIndex: number) {
console.log(`Parameter value: ${target[methodName][parameterIndex]}`);
}

When calling the sayHello method, the logParameter decorator will be executed, and the parameter value will be logged to the console:

const person = new Person('John');
person.sayHello('Have a nice day!'); // Output: Hello, John! Have a nice day!
//         Parameter value: Have a nice day!

Decorators for parameters provide a powerful way to add behavior to functions based on their parameters. They can be used, for example, for input validation, logging, or to modify the behavior of a function based on its arguments.

It’s important to note that decorators for parameters cannot modify the parameter itself. Their primary purpose is to execute code before or after the function is called, and potentially access or analyze the parameter value.

Conclusion

In TypeScript, decorators can be applied to function parameters using the @ syntax. Decorators for parameters allow you to add behavior to functions based on their arguments and are a powerful tool for extending the functionality of your code.

Decorators for Accessors (Getters and Setters) in TypeScript

Accessors, also known as getters and setters, allow us to define the logic that should be executed when reading from or writing to a property in a class. TypeScript decorators can also be applied to accessors, providing additional functionality and customization.

Using Decorators with Getters and Setters

To use decorators with getters and setters, we can simply apply the decorator to the accessor method using the @ syntax. Here is an example:

class Example {
private _value: number = 0;
@decorator
get value(): number {
return this._value;
}
@decorator
set value(newValue: number) {
this._value = newValue;
}
}

In this example, the decorator is applied to both the getter and setter of the `value` accessor. The decorator function will be executed whenever the property is read or written. Note that decorators applied to accessors cannot access the property itself, but only the getter and setter methods.

Decorator Function Signature

The decorator function applied to an accessor should have the following signature:

function decorator(target: any, key: string, descriptor: PropertyDescriptor): void {
// decorator logic here
}

• target: The class prototype or the object instance containing the accessor.
• key: The name of the accessor method.
• descriptor: An object that contains the property descriptor of the accessor.

Example: Logging Access to a Property

One common use case for decorators applied to accessors is logging access to a property. We can create a decorator that logs the name of the property and the accessed value whenever the property is read. Here is an example:

function logAccess(target: any, key: string, descriptor: PropertyDescriptor): void {
const originalMethod = descriptor.get;
descriptor.get = function () {
console.log(`Property ${key} accessed`);
const value = originalMethod.call(this);
console.log(`Value: ${value}`);
return value;
};
}
class Person {
private _name: string;
constructor(name: string) {
this._name = name;
}
@logAccess
get name(): string {
return this._name;
}
}
const person = new Person("John");
console.log(person.name);

In this example, the `logAccess` decorator logs the name of the property being accessed and the accessed value. When we create a new `Person` instance and read the `name` property, the decorator function will be executed and the logs will be printed to the console:

Property name accessed
Value: John
John

Conclusion

Decorators can be applied to accessors (getters and setters) in TypeScript to provide additional functionality and customization. By using decorators with accessors, we can add logic that should be executed when reading from or writing to a property, such as logging access or applying validation. This allows for greater control and extensibility in our TypeScript code.

Decorators for Static Members in TypeScript

In TypeScript, decorators can also be applied to static members of a class. Static members are those that belong to the class itself rather than to an instance of the class.

Defining a Decorator for Static Members

To define a decorator for static members, you can use the same syntax as for instance members. The only difference is that the decorator function is applied to the class constructor itself, rather than to the prototype of the class.

Here is an example of a decorator that logs the value of a static property:

“`typescript

function logStaticProperty(target: any, propertyKey: string) {

const value = target[propertyKey];

console.log(`Static property “${propertyKey}” has value: ${value}`);

}

class MyClass {

@logStaticProperty

static myStaticProperty = 42;

}

“`

In this example, the `logStaticProperty` decorator function takes two arguments: the class constructor (`target`) and the name of the property (`propertyKey`). Inside the decorator function, we can access the value of the static property using `target[propertyKey]`.

When the decorator is applied to the static property `myStaticProperty` of the `MyClass` class, it logs the value of the property to the console: “Static property “myStaticProperty” has value: 42″.

Using Multiple Decorators for Static Members

Just like with instance members, you can apply multiple decorators to static members. The decorators are executed in the order they are defined.

Here is an example of applying multiple decorators to a static method:

“`typescript

function logStaticMethod(target: any, propertyKey: string, descriptor: PropertyDescriptor) {

console.log(`Static method “${propertyKey}” was called`);

}

function measureStaticMethodExecutionTime(target: any, propertyKey: string, descriptor: PropertyDescriptor) {

const originalMethod = descriptor.value;

descriptor.value = function (…args: any[]) {

console.time(propertyKey);

const result = originalMethod.apply(this, args);

console.timeEnd(propertyKey);

return result;

};

return descriptor;

}

class MyClass {

@logStaticMethod

@measureStaticMethodExecutionTime

static myStaticMethod() {

// Some code here

}

}

“`

In this example, the `logStaticMethod` decorator logs a message to the console whenever the static method is called. The `measureStaticMethodExecutionTime` decorator measures the execution time of the static method using `console.time` and `console.timeEnd`.

When the static method `myStaticMethod` is called, it first logs a message to the console: “Static method “myStaticMethod” was called”, and then measures the execution time and logs it to the console.

Summary

Decorators can be used to modify and add behavior to static members of a class in TypeScript. Just like with instance members, decorators for static members can be defined using the same syntax, by applying the decorator function to the class constructor. Multiple decorators can also be applied to static members, and they will be executed in the order they are defined.

Decorators for Method and Parameter Return Types in TypeScript

In TypeScript, decorators provide a way to modify the behavior of a class, method, parameter, or property at runtime. In this article, we will explore decorators for method and parameter return types in TypeScript.

Method Decorators

Method decorators are applied to the methods of a class and allow us to modify the behavior of the method. Decorators are declared by prefixing the method with the @ symbol followed by the decorator name.

Here’s an example of a method decorator that logs the method name and arguments:

“`typescript

function logMethod(target: Object, key: string, descriptor: PropertyDescriptor) {

const originalMethod = descriptor.value;

descriptor.value = function (…args: any[]) {

console.log(`Method ${key} called with args: ${args.join(‘, ‘)}`);

return originalMethod.apply(this, args);

};

return descriptor;

}

class Example {

@logMethod

greet(name: string) {

console.log(`Hello, ${name}!`);

}

}

const example = new Example();

example.greet(“John”); // Output: Method greet called with args: John

“`

In the above example, the `logMethod` decorator modifies the original method by logging the method name and arguments before executing the original method.

Parameter Decorators

Parameter decorators are applied to the parameters of a method or constructor. They allow us to modify or annotate the parameters at runtime. Parameter decorators are declared by prefixing the parameter with the @ symbol followed by the decorator name.

Here’s an example of a parameter decorator that logs the value of a parameter:

“`typescript

function logParameter(target: Object, key: string, parameterIndex: number) {

console.log(`Parameter ${parameterIndex} of method ${key} has value: ${target[key]}`);

}

class Example {

greet(@logParameter name: string) {

console.log(`Hello, ${name}!`);

}

}

const example = new Example();

example.greet(“John”); // Output: Parameter 0 of method greet has value: John

“`

In the above example, the `logParameter` decorator logs the value of the parameter `name` when the `greet` method is called.

Conclusion

Decorators provide a powerful way to modify the behavior of methods and parameter return types in TypeScript. They allow us to add custom functionality or annotations to our code at runtime. Understanding decorators can greatly enhance the flexibility and expressiveness of our TypeScript programs.

Decorators Composition in TypeScript

Decorators are a powerful feature in TypeScript that allows you to add behavior to a class, method, property, or parameter. One of the great advantages of decorators is the ability to compose them together to achieve more complex functionality.

Basic Decorator Composition

To compose decorators in TypeScript, you can simply list them one after the other, applying each decorator sequentially. The output of one decorator becomes the input of the next one.

Here’s an example of how you can compose multiple decorators on a class:

“`typescript

@decorator1

@decorator2

class MyClass {

// class implementation

}

“`

The `MyClass` will first be passed to `decorator1`, and then the output of `decorator1` will be passed to `decorator2`. This allows each decorator to add its own behavior or modify the class in a specific way.

Applying Decorators to Methods and Properties

Decorator composition works similarly for methods and properties. You can apply multiple decorators to a single method or property. The decorators will be executed in the order they are listed.

“`typescript

class MyClass {

@decorator1

@decorator2

method() {

// method implementation

}

}

“`

In this example, `method` will first be passed to `decorator1`, and then the output of `decorator1` will be passed to `decorator2`. This allows you to apply multiple decorators to a single method and chain their behavior.

Order of Execution

It’s important to note that the order of decorator execution is from bottom to top. This means that decorator1 will be executed first, and then the output will be passed to decorator2.

For example:

“`typescript

@decorator2

@decorator1

class MyClass {

// class implementation

}

“`

In this case, `decorator1` will be executed first, and then the output will be passed to `decorator2`. This order is crucial in cases where one decorator depends on the output of another decorator.

Conclusion

Decorators composition is a powerful feature in TypeScript that allows you to combine multiple decorators to enhance the behavior of classes, methods, properties, or parameters. By sequencing decorators, you can achieve more complex functionality and create reusable decorators that can be applied in different combinations.

It’s important to understand the order of execution when composing decorators to ensure the desired behavior.

Built-in Decorators in TypeScript

TypeScript provides several built-in decorators that can be used to modify the behavior of classes, methods, properties, and parameters. Decorators are applied to these elements by using the @ symbol followed by the decorator name.

Class Decorators

• @sealed: The @sealed decorator can be applied to a class to prevent it from being subclassed.
• @deprecated: The @deprecated decorator can be used to mark a class as deprecated, indicating that it should not be used anymore.
• @experimental: The @experimental decorator can be used to mark a class as experimental, indicating that it is subject to change or removal in future versions.

Method Decorators

• @log: The @log decorator can be used to log information about method invocations, such as the method name and arguments.
• @cache: The @cache decorator can be used to cache the result of a method, improving performance by avoiding unnecessary computations.
• @throttle: The @throttle decorator can be used to throttle the execution of a method, ensuring that it is not called too frequently.

Property Decorators

• @readonly: The @readonly decorator can be applied to a property to make it read-only, preventing its value from being modified.
• @observable: The @observable decorator can be used to make a property observable, enabling automatic change detection.
• @validate: The @validate decorator can be used to validate the value of a property, ensuring that it meets certain criteria.

Parameter Decorators

• @required: The @required decorator can be applied to a function parameter to indicate that it is required and must be provided.
• @validate: The @validate decorator can be used to validate the value of a function parameter, ensuring that it meets certain criteria.
• @inject: The @inject decorator can be used to inject a dependency into a function parameter, allowing it to be automatically resolved.

Conclusion

TypeScript provides a variety of built-in decorators that can be used to modify the behavior of classes, methods, properties, and parameters. These decorators allow you to add additional functionality to your code, such as caching, logging, validation, and dependency injection. By leveraging decorators, you can enhance the readability, maintainability, and extensibility of your TypeScript code.

Creating Custom Decorators in TypeScript

In TypeScript, decorators enable us to add additional functionality to classes, methods, properties, or parameters at design-time. TypeScript provides built-in decorators such as @classDecorator, @methodDecorator, etc., but we can also create our own custom decorators.

Defining a Custom Decorator

To define a custom decorator, we need to create a function that takes three arguments: the target object, the property name (optional), and the property descriptor (optional).

The target object represents the prototype of the class for a static member, or the instance of the class for an instance member. The property name is a string that represents the name of the property on which the decorator is applied. The property descriptor holds the attributes of the property.

Here’s an example of a basic custom decorator that logs a message when a method is called:

“`typescript

function logMethod(target: any, propertyKey: string, descriptor: PropertyDescriptor) {

const originalMethod = descriptor.value;

descriptor.value = function (…args: any[]) {

console.log(`Method ${propertyKey} called with arguments:`, args);

const result = originalMethod.apply(this, args);

console.log(`Method ${propertyKey} returned:`, result);

return result;

};

return descriptor;

}

“`

Applying the Custom Decorator

To apply the custom decorator to a class method, we use the @ symbol followed by the name of the decorator function.

Here’s an example of applying the logMethod decorator to a class method:

“`typescript

class Example {

@logMethod

doSomething() {

console.log(‘Doing something…’);

}

}

“`

When the doSomething method is called on an instance of the Example class, the decorator logs the method call and its return value to the console:

“`

Doing something…

Method doSomething called with arguments: []

Method doSomething returned: undefined

“`

Multiple Decorators

Multiple decorators can be applied to the same class, method, property, or parameter. The decorators are applied in the order they are specified, from bottom to top.

If multiple decorators are applied to the same element, the return value of each decorator function is passed as an argument to the next decorator function in the chain.

Summary

Creating custom decorators in TypeScript allows us to enhance the behavior of our classes, methods, properties, or parameters. By defining our own decorator functions, we can easily add reusable functionality to our codebase.

When applying custom decorators, it’s important to keep in mind that the decorator function should conform to the signature function(target: any, propertyKey: string, descriptor: PropertyDescriptor). The target object represents the instance or prototype of the class, the propertyKey is the name of the decorated property, and the descriptor holds the property’s attributes.

With custom decorators, we can achieve a higher level of abstraction and maintainability in our TypeScript projects.

FAQ:

What is a decorator in TypeScript?

A decorator is a special kind of declaration that can be attached to a class declaration, method, accessor, property, or parameter. Decorators are used to modify the behavior of a target declaration.

How can I define a decorator in TypeScript?

To define a decorator, you can create a function or a class that will be used as the decorator. Decorators are applied using the ‘@’ symbol followed by the decorator name.

Can a decorator have arguments?

Yes, a decorator can have arguments. You can pass arguments to a decorator by enclosing them in parentheses after the decorator name, just like you would for a function call.

What are some common use cases for decorators?

Decorators can be used for a variety of purposes, such as logging, performance monitoring, access control, validation, and more. They provide a way to add or modify functionality in a declarative manner.

Can decorators be applied to TypeScript interfaces?

No, decorators can only be applied to class declarations, methods, accessors, properties, and parameters. They are not supported on interfaces in TypeScript.