React Perf Tools

This project includes integration with the performance tools like Lighthouse, Build Analyzer & Size Limit. As a bonus, it also covers performance optimizations using React Profiler, useCallback and useMemo hooks.

Purpose & Benefits

PURPOSE	BENEFITS
To audit the web app from different perspectives e.g. Performance, Best Practices, etc.	Actively monitoring performance helps in avoiding last cycle bottlenecks.
Analysing the bundle size	Reports can help in analysing things visually and take corresponding actions.
Simulates “real-world” circumstances e.g. data network, throttling	Optimized code
Prevent regressions in our site	From failing audits as indicators, we can use to improve the overall web app’s quality.

Lighthouse

Config for lighthouse can be found under lighthouse/config/config.js
reports can be found under lighthouse/reports/----
1. initial.(all) -> these were the reports generated initially

Scripts

yarn run lighthouse

Runs the lighthouse script
and opens the report in browser.

Script Explanation

"lighthouse http://localhost:5000 --config-path=./lighthouse/config/config.js --output json --output html --output-path ./lighthouse/reports/initial --quiet --view --chrome-flags=--headless"

url

http://localhost:5000 - url on which we need to see the metrics.

input

Configuration --config-path=./lighthouse/config/config.js -> Default config can be found here

output

--output json --output html --output-path ./lighthouse/reports/initial ->

--output json --output html -> generates report in json and html format
--output-path -> generates report at the path specific

--quiet -> If you want the report to run silently you can use the following argument

--view -> With the “view” argument, your report opens in a chrome window once after it has finished running

--chrome-flags=--headless -> If you don’t want the Chrome browser pop-up to open we need to provide this argument

--extra-headers=./lighthouse/config/custom-headers.json -> At times, there are some custom headers that are required to be send in http request, these
can be override by this argument

Build Analyzer

source-map-explorer is used as a bundle analyzer as it shows tree map visualization. Whenever, the build size limit exceeds threshold or it is consuming more time then desired threshold. We can analyze the bundle from the modules perseptive which we have integrated and also from the code perspective. We can optimize the respective areas.

Why source-map-explorer?

Analyze and debug JavaScript code through source maps.

Scripts

yarn run analyze

Runs the analyze script
and opens the tree map in browser.

Size Limit

size-limit to budget the app.

Scripts

yarn run size

Runs the analyze script
and shows report as below for pass & fail respectively.

Success

    Time limit:   1.5 s
    Size:         43.4 KB
    Loading time: 868 ms  on slow 3G
    Running time: 446 ms  on Snapdragon 410
    Total time:   1.4 s

Error

    Total time limit has exceeded
    Time limit:   1 s
    Size:         43.4 KB
    Loading time: 868 ms  on slow 3G
    Running time: 398 ms  on Snapdragon 410
    Total time:   1.3 s

References

Type	Description	URL
Lighthouse Developer API	This is an API reference for Lighthouse.	Google Docs
Lighthouse CLI Configuration	Configurations explained for Lighthouse CLI.	Repo's README.md File
Lighthouse Code repo	GIT repo link to Lighthouse.	Github Repo
Lighthouse Scoring & Terms Explained	Docs link which can explain insights about how scores are calculated.	Repo's README.md File
Chrome Flags	List of Chromium Command Line Switches --headless used at the top.	Link to refer Chrome Flags
source-map-explorer	details about the package, scripts & arguments to refer.	Link to refer NPM package