depalyzer

A tool which determines whether an npm module modifies the built-in javascript types like Array, Object, etc.

Installation

You can either install depalyzer globally:

sudo npm install -g depalyzer

This allows you to use it like traditional binary:

depalyzer true-html-escape

Or install it locally:

npm install depalyzer

And run it as follows:

./node_modules/.bin/depalyzer true-html-escape

Usage

depalyzer [--verbose] module-name

• module-name: the name of the npm module to be analyzed
• --verbose: optionally enable detailed output

Output

For a module with > 1 modification to build-in types, the script will exit with the code 1 and you'll see output like:

padowan@pure-deps> depalyzer true-html-escape
true-html-escape includes 3 dependencies...
✓ 3 globals were not modified.
   ✓ Object.prototype
   ✓ Boolean.prototype
   ✓ Math
✗ FAILURE: 10 globals were modified, with 623 total modifications.
   ✗ Array
   ✗ Array.prototype
   ✗ Object
   ✗ Number
   ✗ Number.prototype
   ✗ Function
   ✗ Function.prototype
   ✗ Boolean
   ✗ Date
   ✗ Date.prototype

For a module without modifications, the script will exit with code 0 and you'll see output like:

padowan@pure-deps> depalyzer escape-html
escape-html includes 0 dependencies...
✓ Success: No globals were modified.
   ✓ Array
   ✓ Array.prototype
   ✓ Object
   ✓ Object.prototype
   ✓ Number
   ✓ Number.prototype
   ✓ Function
   ✓ Function.prototype
   ✓ Boolean
   ✓ Boolean.prototype
   ✓ Date
   ✓ Date.prototype
   ✓ Math

Why?

It's hard to know what you'll get when you install a new npm module. This tool allows you to quickly check for modules which modify the built-in types, like the 623 additions and modifications made by the true-html-escape library to types like Array and Date.

These can and do have real side-effects on your software. This tool helps developers avoid those side-effects.

May the force be with you in your journey for pure dependencies young padowan.

What's next:

• Tests!

• Expand the types which are monitored for mutations

• Options for disabling color, fancy checks n' such

• Expose API for programmatic use, something like:

  const depalyzer = require('depalyzer');
  const results = depalyzer('true-html-escape');
  if (results.hasGlobalModifications()) {
    console.error('Oh noes!')
  }