Rename 'performance' to 'benchmarks'

benchmarks/benchmark.js

@@ -0,0 +1,97 @@
+import * as marky from 'marky';
+
+const fmt = time => `${Math.round(time * 100) / 100}ms`;
+
+const measure = (name, fn) => {
+  marky.mark(name);
+  fn();
+  const performanceMeasure = marky.stop(name);
+  return performanceMeasure.duration;
+};
+
+const mean = values => {
+  const sum = values.reduce((sum, value) => sum + value, 0);
+  return sum / values.length;
+};
+
+const median = values => {
+  if (!Array.isArray(values)) {
+    return 0;
+  }
+  if (values.length === 1) {
+    return values[0];
+  }
+
+  const numbers = [...values].sort((a, b) => a - b);
+  return (numbers[(numbers.length - 1) >> 1] + numbers[numbers.length >> 1]) / 2;
+};
+
+const standardDeviation = values => {
+  const avg = mean(values);
+
+  const squareDiffs = values.map(value => {
+    const diff = value - avg;
+    return diff * diff;
+  });
+
+  const meanSquareDiff = mean(squareDiffs);
+  return Math.sqrt(meanSquareDiff);
+};
+
+const benchmark = ({ name, description, setup, teardown, task, runs }) => {
+  return new Promise(resolve => {
+    const durations = [];
+    let i = 0;
+
+    setup();
+    const first = measure('first', task);
+    teardown();
+
+    const done = () => {
+      const stdDev = standardDeviation(durations);
+      const formattedFirst = fmt(first);
+      const formattedMean = fmt(mean(durations));
+      const formattedMedian = fmt(median(durations));
+      const formattedStdDev = fmt(stdDev);
+
+      console.groupCollapsed(`${name}\n${formattedMean} ±${fmt(2 * stdDev)}`);
+      description && console.log(description);
+      console.log(`First: ${formattedFirst}`);
+      console.log(`Median: ${formattedMedian}`);
+      console.log(`Mean: ${formattedMean}`);
+      console.log(`Standard deviation: ${formattedStdDev}`);
+      console.log(durations);
+      console.groupEnd();
+      resolve();
+    };
+
+    const a = () => {
+      setup();
+      window.requestAnimationFrame(b);
+    };
+
+    const b = () => {
+      const duration = measure('mean', task);
+      durations.push(duration);
+      window.requestAnimationFrame(c);
+    };
+
+    const c = () => {
+      teardown();
+      window.requestAnimationFrame(d);
+    };
+
+    const d = () => {
+      i += 1;
+      if (i < runs) {
+        window.requestAnimationFrame(a);
+      } else {
+        window.requestAnimationFrame(done);
+      }
+    };
+
+    window.requestAnimationFrame(a);
+  });
+};
+
+export default benchmark;