feat: add JSON Reporter

README.md

@@ -237,6 +237,46 @@ const suite = new Suite({
 });
 ```
 
+### `jsonReport`
+
+The `jsonReport` plugin provides benchmark results in **JSON format**.  
+It includes key performance metrics—such as `opsSec`, `runsSampled`, `min`
+and `max` times, and any reporter data from your **plugins**—so you can easily
+store, parse, or share the information.
+
+Example output:
+
+```json
+[
+  {
+    "name": "single with matcher",
+    "opsSec": 180000,
+    "runsSampled": 50,
+    "min": "13.20μs",
+    "max": "82.57μs",
+    "plugins": []
+  },
+  {
+    "name": "Multiple replaces",
+    "opsSec": 170000,
+    "runsSampled": 50,
+    "min": "15.31μs",
+    "max": "77.49μs",
+    "plugins": []
+  }
+]
+```
+
+**Usage:**
+
+```cjs
+const { Suite, jsonReport } = require('bench-node');
+
+const suite = new Suite({
+  reporter: jsonReport,
+});
+```
+
 ### Custom Reporter
 
 Customize data reporting by providing a `reporter` function when creating the `Suite`:

examples/json-report/node.js

@@ -0,0 +1,21 @@
+const { Suite, jsonReport } = require('../../lib');
+const assert = require('node:assert');
+
+const suite = new Suite({
+  reporter: jsonReport,
+});
+
+suite
+  .add('single with matcher', function () {
+    const pattern = /[123]/g
+    const replacements = { 1: 'a', 2: 'b', 3: 'c' }
+    const subject = '123123123123123123123123123123123123123123123123'
+    const r = subject.replace(pattern, m => replacements[m])
+    assert.ok(r);
+  })
+  .add('Multiple replaces', function () {
+    const subject = '123123123123123123123123123123123123123123123123'
+    const r = subject.replace(/1/g, 'a').replace(/2/g, 'b').replace(/3/g, 'c')
+    assert.ok(r);
+  })
+  .run();

lib/index.js

@@ -2,7 +2,12 @@ const { Worker } = require('node:worker_threads');
 const { types } = require('node:util');
 const path = require('node:path');
 
-const { textReport, chartReport, htmlReport } = require('./report');
+const {
+  textReport,
+  chartReport,
+  htmlReport,
+  jsonReport,
+} = require('./report');
 const { getInitialIterations, runBenchmark, runWarmup } = require('./lifecycle');
 const { debugBench, timer, createFnString } = require('./clock');
 const {
@@ -203,4 +208,5 @@ module.exports = {
   chartReport,
   textReport,
   htmlReport,
+  jsonReport,
 };

lib/report.js

@@ -1,9 +1,11 @@
 const { textReport } = require('./reporter/text');
 const { chartReport } = require('./reporter/chart');
 const { htmlReport } = require('./reporter/html');
+const { jsonReport } = require('./reporter/json');
 
 module.exports = {
   chartReport,
   textReport,
   htmlReport,
+  jsonReport,
 };

lib/reporter/json.js

@@ -0,0 +1,28 @@
+'use strict'
+
+const { timer } = require('../clock')
+
+function jsonReport (results) {
+  const output = results.map((result) => {
+    const opsSecReported =
+      result.opsSec < 100
+        ? result.opsSec.toFixed(2)
+        : result.opsSec.toFixed(0)
+
+    return {
+      name: result.name,
+      opsSec: Number(opsSecReported),
+      runsSampled: result.histogram.samples,
+      min: timer.format(result.histogram.min),
+      max: timer.format(result.histogram.max),
+      // Report anything the plugins returned
+      plugins: result.plugins.map((p) => p.report).filter(Boolean)
+    }
+  })
+
+  console.log(JSON.stringify(output, null, 2))
+}
+
+module.exports = {
+  jsonReport
+}

test/reporter.js

@@ -2,7 +2,12 @@ const { describe, it, before } = require('node:test');
 const assert = require('node:assert');
 const fs = require('node:fs');
 
-const { Suite, chartReport, htmlReport } = require('../lib');
+const {
+  Suite,
+  chartReport,
+  htmlReport,
+  jsonReport,
+} = require('../lib');
 
 describe('chartReport outputs benchmark results as a bar chart', async (t) => {
   let output = '';
@@ -107,3 +112,68 @@ describe('htmlReport should create a file', async (t) => {
     assert.ok(htmlContent.includes('}}') === false);
   });
 });
+
+describe('jsonReport should produce valid JSON output', async () => {
+  let output = ''
+
+  before(async () => {
+    const originalStdoutWrite = process.stdout.write
+    process.stdout.write = function (data) {
+      output += data
+    }
+
+    // Create a new Suite with the JSON reporter
+    const suite = new Suite({
+      reporter: jsonReport
+    })
+
+    suite
+      .add('single with matcher', function () {
+        const pattern = /[123]/g
+        const replacements = { 1: 'a', 2: 'b', 3: 'c' }
+        const subject = '123123123123123123123123123123123123123123123123'
+        const r = subject.replace(pattern, (m) => replacements[m])
+        assert.ok(r)
+      })
+      .add('Multiple replaces', function () {
+        const subject = '123123123123123123123123123123123123123123123123'
+        const r = subject.replace(/1/g, 'a').replace(/2/g, 'b').replace(/3/g, 'c')
+        assert.ok(r)
+      })
+
+    // Run the suite
+    await suite.run()
+
+    // Restore stdout
+    process.stdout.write = originalStdoutWrite
+  });
+
+  it('should print valid JSON', () => {
+    // Verify if the output can be parsed as JSON
+    let data
+    try {
+      data = JSON.parse(output)
+    } catch (err) {
+      assert.fail(`Output is not valid JSON: ${err.message}`)
+    }
+
+    assert.ok(Array.isArray(data), 'Output should be an array of results')
+  });
+
+  it('should contain the required benchmark fields', () => {
+    const data = JSON.parse(output)
+
+    // We expect the two benchmarks we added: 'single with matcher' and 'Multiple replaces'
+    assert.strictEqual(data.length, 2, 'Should have results for 2 benchmarks')
+
+    for (const entry of data) {
+      // Ensure each entry has expected keys
+      assert.ok(typeof entry.name === 'string', 'name should be a string')
+      assert.ok(typeof entry.opsSec === 'number', 'opsSec should be a number')
+      assert.ok(typeof entry.runsSampled === 'number', 'runsSampled should be a number')
+      assert.ok(typeof entry.min === 'string', 'min should be a string (formatted time)')
+      assert.ok(typeof entry.max === 'string', 'max should be a string (formatted time)')
+      assert.ok(Array.isArray(entry.plugins), 'plugins should be an array')
+    }
+  });
+});