@namchee/decora/src/benchmark.ts

Useful ECMAScript-compliant decorators to enhance JS (specifically, TypeScript) development experience

import { isNode, isBrowser } from './utils';

/**
 * Apply simple benchmarking to a method,
 * which will logged to `console`.
 * @param {'s' | 'ms' | 'ms'} metric - time metric to be used.
 * Defaults to `ms`
 * @param {number?} precision - time precision to be shown on
 * log. Passing `undefined` will log an abruptly long number string.
 * @return {Function} - modified function with benchmark capabilities
 */
export function benchmark(
  metric: 's' | 'ms' | 'ns' = 'ms',
  precision?: number,
  stream: NodeJS.WritableStream = process.stdout,
): Function {
  return function(
    target: Object,
    keyName: string,
    descriptor: PropertyDescriptor,
  ): void {
    if (!descriptor || !(descriptor.value instanceof Function)) {
      throw new Error(
        '@benchmark decorator can only be applied to functions',
      );
    }

    let logger: Console;
    let performance: Performance;

    if (isNode) { // node environment
      const Console = require('console').Console;

      logger = new Console({ stdout: stream });
      performance = require('perf_hooks').performance;
    } else if (isBrowser) { // browser
      logger = window.console;
      performance = window.performance;

      // if stream is somehow defined, ignore it
      if (stream) {
        logger.warn(
          /* eslint-disable-next-line */
          'The `stream` option only available on Node.JS environment. This option will be ignored.',
        );
      }
    } else { // do nothing, for now
      return;
    }

    const fn: Function = descriptor.value;

    descriptor.value = async function(...args: any[]) {
      const start = performance.now();

      const result = await fn.apply(this, args);

      const end = performance.now();
      let diff = end - start;

      if (metric !== 'ms') {
        diff = metric === 's' ?
          diff / 1000 :
          diff * 1000;
      }

      logger.info(
        /* eslint-disable-next-line */
        `Function ${keyName} from class ${target.constructor.name} was executed in ${diff.toFixed(precision)} ${metric}`,
      );

      return result;
    };
  };
}