page-timing

⏱ Collect and measure browser performance metrics

All metrics are converted to snake_case

import { navigation, paint } from 'page-timing';

(async () => {
    const results = await Promise.all([
        paint(),
        navigation()
    ]);

    const metrics = Object.assign(...results);

    fetch('/browser-performance-metrics', {
        method: 'POST',
        body: JSON.stringify({
            page_name: 'my page',
            metrics
        }),
    });
})();

API endpoints

• navigation: Navigation Timing Illustration 🎨
• paint: Paint Timing
• assets: Information about page resources when this function is called
• connection: Network Information
• memory: Memory API information
• display: Screen and document information
• dom: Calculated metrics from the document object
• elapsed: Time when the measurements were taken
• all: A compound object containing all of the above
• measure: A helper function: Add measure entries to navigation timing API

Metrics

Name	Meaning	Group	Type
navigation_start	Termination of previous document upon navigating	navigation	number
unload_event_start	Previous document unload	navigation	number
unload_event_end		navigation	number
redirect_count	Numbers of redirects while requesting this page	navigation	number
redirect_start	Redirect from previous document	navigation	number
redirect_end		navigation	number
fetch_start	Ready to fetch the document	navigation	number
domain_lookup_start		navigation	number
domain_lookup_end		navigation	number
duration	Difference between responseEnd and startTime	navigation	number
connect_start	Sent request to open a connection	navigation	number
connect_end		navigation	number
secure_connection_start	Secure connection handshake	navigation	number
request_start	Request the document	navigation	number
response_start	Received the first byte of the response	navigation	number
response_end	Received the last byte of the response	navigation	number
dom_loading	Parser started work	navigation	number
dom_interactive	Parser finished work on main document. Changed document readyState to "interactive"	navigation	number
dom_content_loaded_event_start	Executed required scripts after parsing the document	navigation	number
dom_content_loaded_event_end		navigation	number
dom_complete	Changed document readyState to "complete"	navigation	number
load_event_start	All assets are loaded. Document fires "load" event	navigation	number
load_event_end	Document finished executing "load" event listeners	navigation	number
transfer_size	Size (octets) of response headers and payload body	navigation	number
encoded_body_size	Size (octets) of payload body	navigation	number
decoded_body_size	Size (octets) of message body	navigation	number
worker_start	Time until service worker ran	navigation	number
first_paint	User agent first rendered after navigation	paint	number
first_contentful_paint	Document contains at least one element that is paintable and contentful †	paint	number
first_image_paint	TBD	paint	number
final_asset_javascript_count	Total number of Javascript resources	assets	number
final_asset_javascript_load	Loading time spent on Javascript resources	assets	number
final_asset_javascript_size	Total size of Javascript resources	assets	number
final_asset_stylesheets_count	Total number of CSS resources	assets	number
final_asset_stylesheets_load	Loading time spent on CSS resources	assets	number
final_asset_stylesheets_size	Total size of CSS resources	assets	number
final_asset_images_count	Total number of image resources	assets	number
final_asset_images_load	Loading time spent on image resources	assets	number
final_asset_images_size	Total size of image resources	assets	number
final_asset_other_count	Total number of other resources	assets	number
final_asset_other_load	Loading time spent on other resources	assets	number
final_asset_other_size	Total size of other resources	assets	number
connection_type	bluetooth, cellular, ethernet, none, wifi, wimax, other, unknown	connection	string
effective_bandwidth	Mbps	connection	number
effective_connection_type	slow-2g, 2g, 3g, 4g	connection	string
effective_max_bandwidth	Mbps	connection	number
reduced_data_usage	Vendor's "Data Saver" feature enables	connection	boolean
round_trip_time	Estimated effective round-trip in ms	connection	number
navigation_type	navigate, reload, back_forward, prerender	connection	string
js_heap_size_limit	Maximum bytes available for JS heap	memory	number
total_js_heap_size	Total allocated bytes for JS heap	memory	number
used_js_heap_size	Currently active bytes of JS heap	memory	number
window_inner_height	Height of the window's layout viewport	display	number
window_inner_width	Width of the window's layout viewport	display	number
screen_color_depth	Color depth of the screen	display	number
screen_pixel_depth	Bit depth of the screen	display	number
screen_orientation_type	landscape-primary, landscape-secondary, portrait-primary, portrait-secondary	display	string
final_dom_node_count	Total number of nodes under the document object	dom	number
final_dom_nest_depth	Highest nesting depth of DOM element under the document	dom	number
final_html_size	Character count of the HTML document	dom	number
page_time_elapsed	milliseconds elapsed since the time origin	elapsed	number

† contentful element: A visible element which contains non empty text, media content or input.

More functions

fps

Measure page frame rate at a certain point in time

import { fps } from 'page-timing';

const frames_per_second = await fps();
console.log({ frames_per_second });

Increase sample rate by checking more than one second. (Result is still in frames per second)

const frames_per_second = await fps({ sample: 5 });
console.log({ frames_per_second });

measure

Wrap a function and measure it's execution time in milliseconds into a performance measure entry.

import { measure } from 'page-timing';

async function myFunction(
    await wait(50);
    doSomethingElse();
}

await measure(myFunction, 'my-function');

// Example: Convert entries to a named array
Object.assign(
    ...performance.getEntriesByType('measure').map(
        ({ name, duration }) => ({[name]: duration})
    )
);
// {my-function: 53.35999990347773}

// Example: Retrieve a specific entry
const { duration } = performance.getEntriesByName('my-function');
// 53.35999990347773

Illustration of navigation events

Bonus

A simple example to add web vitals and TTI

npm i page-timing web-vitals tti-polyfill

import { all, connection } from 'page-timing';
import { getLCP, getFID, getCLS } from 'web-vitals';
import TTI from 'tti-polyfill';

(async () => {
    const connectionInfo = await connection();

    // Send metrics from browser performance API
    send(await all());

    // Send web vitals to the same endpoint
    [
        [getLCP, 'largest_contentful_paint'],
        [getFID, 'first_input_delay'],
        [getCLS, 'cumulative_layout_shift'],
    ].forEach(
        ([ fn, name ]) => fn(
            ({ value }) => send({
                [name]: value,
                ...connectionInfo // Some connection info
            })
        )
    );

    TTI.getFirstConsistentlyInteractive().then(
        (time_to_interactive) => send({
            time_to_interactive,
            ...connectionInfo // Some connection info
        })
    ).catch(() => null)
})();

const send = metrics => fetch('/browser-performance-metrics', {
  method: 'POST',
  body: JSON.stringify({ page_name: 'my page', metrics }),
});