Dosa

1.0.0 verified Fri May 01 auth: no javascript

Dosa is a JavaScript AST transpiler for instrumentation, wrapping variable accesses, function calls, binary expressions, and string literals with custom box_* functions. Version 1.0.0 is the initial stable release with no active development. It uses UglifyJS under the hood to parse and transform code, targeting debugging or runtime monitoring. Unlike Babel plugins or other instrumentation libraries, Dosa focuses on a simple, predictable transformation pattern, making it suitable for lightweight tracing but limited in customization.

Common errors

error Cannot find module 'uglify-js' ↓

cause Missing peer dependency uglify-js

fix

Run npm install uglify-js alongside dosa.

error TypeError: dosa.instrument is not a function ↓

cause Using require('dosa') which returns an object, not the instrument function directly

fix

Use const dosa = require('dosa'); dosa.instrument(input); or ES6 import.

Warnings

gotcha Instrumentation wraps all function calls and property accesses, which can break performance and runtime behavior if not expected. ↓

fix Use only in development or debugging contexts; do not use in production without profiling.

gotcha The package does not handle dynamic eval() or with() statements; they will be passed through unchanged without instrumentation. ↓

fix Avoid using eval() or with() in source code to ensure consistent instrumentation.

deprecated No longer maintained; last release 2018. Consider using @babel/plugin-transform-runtime or custom Babel plugin for more robust instrumentation. ↓

fix Migrate to a maintained alternative like babel-plugin-istanbul or a custom Babel plugin.

Install

npm install dosa

yarn add dosa

pnpm add dosa

Imports

dosa (default)
wrong
```
const dosa = require('dosa')
```
correct
```
import dosa from 'dosa'
```
Package does not ship TypeScript types; use @types/dosa if available. Default export is a function with an `instrument` method.

instrument

wrong

const instrument = require('dosa').instrument

correct

import { instrument } from 'dosa'

Named export available since v1.0.0.

DosaOptions
wrong
```
import { DosaOptions } from 'dosa'
```
correct
```
import type { DosaOptions } from 'dosa'
```
Not available in v1.0.0; options are untyped. Use JSDoc for type safety.

Quickstart

Demonstrates basic usage: import the instrument function, pass JavaScript source code, get instrumented output with wrapped calls and string literals.

import { instrument } from 'dosa';

const input = "var a = location.hash.split('#')[1]";
const output = instrument(input);
console.log(output);
// 'var a = box_accessor(box_call(location.hash.split(box_string("#"))), 1);'