v8-deopt-webapp

Display the V8 optimizations and deoptimizations of a JavaScript file

Installation

Check out v8-deopt-viewer for a CLI that automates this for you!

npm i v8-deopt-webapp

Usage

1. Generate a PerFileDeoptInfoWithSources object:

   1. Use v8-deopt-generate-log and v8-deopt-parser to generate a V8DeoptInfo object.

   2. Use the groupByFile utility from v8-deopt-parser to group the results by file.

   3. Extend the resulting object with the source of each file listed, and the shortened relative path to that file (can be defined relative to whatever you like)

      import { parseV8Log, groupByFile } from "v8-deopt-parser";
      
      const rawDeoptInfo = await parseV8Log(logContents);
      const groupDeoptInfo = groupByFile(rawDeoptInfo);
      const deoptInfo = {
          ...groupDeoptInfo,
          // Define some addSources function that adds the `src` and `relativePath` property
          // to each file object in groupDeoptInfo.files
          files: await addSources(groupDeoptInfo.files),
      };
      

2. Include the object in an HTML file

3. Include dist/v8-deopt-webapp.css and dist/v8-deopt-webapp.js in the HTML file

4. Call V8DeoptViewer.renderIntoDom(object, container) with the object and the DOM Node you want the app to render into

Currently, we only produce a UMD build, but would consider publishing an ESM build if it's useful to people

Contributing

See the Contributing.md guide at the root of the repo for general guidance you should follow.

To run the webapp locally:

1. cd into this package's directory (e.g. packages/v8-deopt-webapp)
2. Run node test/generateTestData.mjs
3. Open test/index.html in your favorite web browser

By default, the test page (test/index.html) loads the data from test/deoptInfo.js. If you want to simulate a log that doesn't have sources, add ?error to the URL to load deoptInfoError.js.

If you make changes to v8-deopt-generate-log or v8-deopt-parser, you'll need to rerun generateTestData.mjs to re-generate deoptInfo.js & deoptInfoError.js.