What are decorators in JavaScript and can you give me some examples?

What are decorators in JavaScript and can you give me some examples?

Decorators in JavaScript are special functions that can modify the behavior of classes or methods. For example, you can use a decorator to log method calls or to validate input.

Can you show me a simple example of a method decorator?

Sure! Here's a simple method decorator that logs the execution time of a method:

function logExecutionTime(target, key, descriptor) {
    const originalMethod = descriptor.value;
    descriptor.value = function(...args) {
        const start = performance.now();
        const result = originalMethod.apply(this, args);
        const end = performance.now();
        console.log(`Execution time for ${key}: ${end - start} ms`);
        return result;
    };
    return descriptor;
}

How do I apply this decorator to a method?

You can apply the decorator by prefixing your method with the @logExecutionTime syntax. For example:

class Example {
    @logExecutionTime
    someMethod() {
        // method logic
    }
}

Are there any built-in decorators in JavaScript?

JavaScript itself doesn't have built-in decorators, but they are a proposed feature in ECMAScript. Libraries like TypeScript and some frameworks provide decorator support.