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istanbul-lib-instrument
Advanced tools
The 'istanbul-lib-instrument' package is a core library for instrumenting JavaScript code for coverage analysis. It is part of the Istanbul toolset, which is widely used for code coverage reporting in JavaScript projects. The library provides functionality to instrument code, which means it adds additional code to track which parts of the original code are executed during a test run.
Instrumenting Code
This feature allows you to instrument JavaScript code. The `createInstrumenter` function creates an instrumenter instance, which can then be used to instrument code synchronously using the `instrumentSync` method. The instrumented code will include additional statements to track execution.
const { createInstrumenter } = require('istanbul-lib-instrument');
const instrumenter = createInstrumenter();
const originalCode = 'function add(a, b) { return a + b; }';
const instrumentedCode = instrumenter.instrumentSync(originalCode, 'filename.js');
console.log(instrumentedCode);
Generating Coverage Maps
This feature allows you to generate a coverage map for the instrumented code. After instrumenting the code, you can call the `lastFileCoverage` method to get a coverage map, which provides detailed information about which parts of the code were executed.
const { createInstrumenter } = require('istanbul-lib-instrument');
const instrumenter = createInstrumenter();
const originalCode = 'function add(a, b) { return a + b; }';
instrumenter.instrumentSync(originalCode, 'filename.js');
const coverageMap = instrumenter.lastFileCoverage();
console.log(coverageMap);
NYC is a command-line interface for Istanbul. It provides a higher-level interface for running tests and generating coverage reports. While 'istanbul-lib-instrument' is focused on the low-level task of instrumenting code, NYC provides a more user-friendly way to integrate coverage reporting into your workflow.
Babel-plugin-istanbul is a Babel plugin that instruments code using Istanbul. It is designed to work with Babel, making it easy to integrate code coverage into projects that use Babel for transpilation. This plugin is useful if you are already using Babel and want to add coverage instrumentation as part of your build process.
C8 is a code coverage tool that uses V8's built-in coverage collection. It provides a modern alternative to Istanbul-based tools by leveraging the native coverage capabilities of the V8 JavaScript engine. C8 can be a good choice if you are looking for a tool that integrates closely with Node.js and V8.
FAQs
Core istanbul API for JS code coverage
The npm package istanbul-lib-instrument receives a total of 38,413,846 weekly downloads. As such, istanbul-lib-instrument popularity was classified as popular.
We found that istanbul-lib-instrument demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 0 open source maintainers collaborating on the project.
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