JavaScript装饰者HOWTO？

function logger(fn) {
  return function() {
    console.log(fn.apply(this, arguments));
  };
}

const log = logger(console.log);

log('Hello, world!');

function timer(fn) {
  return function() {
    const startTime = performance.now();
    const result = fn.apply(this, arguments);
    const endTime = performance.now();
    console.log(`Call ${fn.name} took ${endTime - startTime} ms`);
    return result;
  };
}

const slowAdd = timer(function() {
  return 1 + 1;
});

const fastAdd = timer(function() {
  return 1 + 1;
});

const startTime = performance.now();
const result1 = slowAdd();
const result2 = fastAdd();
const endTime = performance.now();
console.log(`Slow add took ${endTime - startTime} ms, result: ${result1}`);
console.log(`Fast add took ${endTime - startTime} ms, result: ${result2}`);