Can someone help me understand the various parameters of a Typescript decorator?
function myDecorator(target) {
// do something with 'target' ...
}In the given example, I am aware that 'target' represents the function/class to which the decorator is applied. However, I am curious about the other parameters of decorators, their significance, and order. It would be great if someone could provide a link to official documentation explaining this.
Thank you in advance.
When using a decorator, it expects an argument which is the target being decorated along with additional arguments based on the type of the target.
For Method Decorators:
The method decorator expression is called as a function during runtime and takes three arguments:
- The constructor function of the class for a static member or the prototype of the class for an instance member.
- The name of the member.
- The Property Descriptor for the member.
You can refer to TypeScript Decorators for a complete list of all decorator types:
Class Decorators
Method Decorators
Accessor Decorators
Property Decorators
Parameter Decorators
In addition:
If we wish to customize how a decorator is applied to a declaration, we can create a decorator factory. A Decorator Factory is essentially a function that returns the expression to be executed by the decorator at runtime.
You have the freedom to create decorator factories with parameters as needed; there are no limitations or restrictions imposed.
The examples provided are from the TypeScript documentation.
Example of a Decorator:
function sealed(target) {
// perform actions on 'target' ...
}
Applied using:
@sealed x
Example of a Decorator Factory:
function color(value: string) {
// this serves as the decorator factory
return function (target) {
// this represents the actual decorator
// perform actions involving 'target' and 'value'...
};
}
Usage:
@color('blue') x
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