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Readme: js-features-analyser

A Node.js command-line application for figuring out what standard-library features are being used within a JavaScript file.

NPM version
MIT licensed

> npx @financial-times/js-features-analyser analyse --file bundle.js

Table Of Contents


This project requires Node.js 10.x and npm. You can install with:

npm install @financial-times/js-features-analyser


This project does not compile syntax at all.

Create a bundle which targets the syntax level you support (ES3/5/2017/2019) and then pass that bundle through this tool.

The reason to create the bundle first is because if you are compiling your code down to another syntax level, the compiled code will contain different built-ins than the uncompiled version. E.G. Compiling async function() { await 7;} to ES5 will make the compiled output have Promise in it, which this tool will then detect.

This project does not know the types that are within the code being analysed, which means that when it sees a name of a builtin being used, it will add all the builtins which match that name to it's output. E.G. Analysing [1].reduce(function(){}) will not only detect that Array.prototype.reduce was used, it would also incorrectly detect that Int8Array.prototype.reduce, Uint8Array.prototype.reduce, Uint8ClampedArray.prototype.reduce, Int16Array.prototype.reduce, Uint16Array.prototype.reduce, Int32Array.prototype.reduce, Uint32Array.prototype.reduce, Float32Array.prototype.reduce, and Float64Array.prototype.reduce were also used.


This module has a full suite of unit tests, and is verified with ESLint. You can use the following commands to check your code before opening a pull request:

npm test    # verify JavaScript code with ESLint and run the tests


New versions of the module are published automatically by CI for every commit which lands on the master branch.


If you have any questions or comments about this module, or need help using it, please raise an issue.


This software is under the MIT licence.

maintained Origami v1 (Bower)
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GitHub: js-features-analyser