I've created a typescript decorator factory that logs the total time taken to execute a function, along with the actual function execution results and parameters passed to the decorator.
For example:
export function performanceLog(...args: any[]) {
return (target: Object, key: string, descriptor: TypedPropertyDescriptor<any>) => {
var msg = '';
if (args.length != 0) {
msg = args.map(arg => arg).join(' ');
}
if (descriptor === undefined) {
descriptor = Object.getOwnPropertyDescriptor(target, key);
}
if (typeof descriptor.value !== 'function') {
throw new SyntaxError('Only functions can be used with log decorators');
}
var originalMethod = descriptor.value.bind(target);
descriptor.value = function() {
var funcArgs: any = [];
for (var i = 0; i < arguments.length; i++) {
funcArgs[i - 0] = arguments[i];
}
var startTime = performance.now();
console.log(`Begin function ${key} with params (${funcArgs}) : ${msg}`);
var result = originalMethod.apply(this, funcArgs);
var endTime = performance.now();
console.log(`End function ${key}. Execution time: ${endTime - startTime} milliseconds. Return result : ${result}`);
return result;
};
return descriptor;
};
}
I'm currently using this decorator with a function within a class: (assuming my class has other methods such as ctor, get, set, and utils).
class LoggerService {
@performanceLog('validate', 'message')
handleMessage(message) {
console.log(message);
return true;
};
}
The function call looks like this:
handleMessage('decoratorValidation');
This gives me the following output:
Begin function handleMessage with params (decoratorValidation) : validate message
decoratorValidation
End function handleMessage. Execution time: 0.3000000142492354 milliseconds.
Return result : true
However, when I try to change the function handleMessage to use arrow function format (ES6), it throws an error:
@performanceLog('validate', 'message')
handleMessage = message => {
console.log(message);
return true;
};
Error Message:
Unable to resolve signature of property decorator when called as an expression.
I have ensured that all parameters are correctly configured in my tsconfig.json file. My entire project is targeted towards "ES6" and I would like the decorator to support arrow functions.