`performance.mark` with metadata is useful for Real user monitoring

I've created performance-mark-metadata.
This library provide performance.mark with custom meta data.

This library inspired by User Timing API Level 3 proposal.
This proposal will add details as metadata to performance.mark.

Currently, Performance.mark() API can not add metadata to marking.

Supports

Modern browser and Node.js >= 8.5.0
They are supported Performance.mark() API.
Performance Timing API | Node.js v9.2.0 Documentation

Old browser need to Performance.mark() polyfill.

nicjansma/usertiming.js: UserTiming polyfill

Install

Install with npm:

npm install performance-mark-metadata

Example

import { PerformanceMetadataMarker } from "performance-mark-metadata";
const marker = new PerformanceMetadataMarker();
const metadata = {
    details: { key: "value" }
};
const markerName = "name";
// mark with metadata
marker.mark(markerName, metadata);
performance.getEntriesByName(markerName).forEach(entry => {
    // get metadata for entry
    const result = marker.getEntryMetadata(entry);
    /*
    {
        details: { key: "value" }
    };
    */
    assert.strictEqual(result, metadata, "should get same metadata");
});

Usage in Node.js

Node.js 8.5.0 introduce perf_hooks module.
You can use this library by passing require("perf_hooks").performance to PerformanceMetadataMarker constructor arguments.

import { PerformanceMetadataMarker } from "performance-mark-metadata";
const nodePerformanceHook = require("perf_hooks");
const performance = nodePerformanceHook.performance;
const marker = new PerformanceMetadataMarker({
    performance
});
marker.mark("name", {
    details: { key: "value" }
});

UseCase

This example show actual usage.

See https://azu.github.io/performance-mark-metadata

You want to found performance problem on viewing the site.
You can analyze the problem by using performance-mark-metadata.

It is useful for Real user monitoring(RUM).
In development, you can use browser's development tools, but it is difficult about RUM.

Mark points

Mark current Frame Per Seconds(FPS)
Mark each action like "onClick"

Record FPS

const { PerformanceMetadataMarker } = require("performance-mark-metadata");
const marker = new PerformanceMetadataMarker();

const FpsEmitter = require("fps-emitter");
const fps = new FpsEmitter();
fps.on("update", function(FPS) {
    // mark current FPS
    marker.mark("FPS", {
        details: {
            FPS: FPS
        }
    });
});

and record action

// heavy task
const heavyTaskButton = document.getElementById("js-button");
heavyTaskButton.addEventListener("click", () => {
    marker.mark("Heavy Action");

    // ... heavy task ...
})

After that, you can get FPS and action logs.

const logData = performance.getEntriesByType("mark").map(entry => {
    const meta = marker.getEntryMetadata(entry);
    return {
        type: entry.name,
        timeStamp: entry.startTime,
        meta: meta
    };
});