tessl/npm-license-checker

Check license info for a package and its dependencies

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Overview

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Output Formatting

Name: tessl/npm-license-checker
Author: tessl

Flexible output formatting system supporting multiple formats for different integration needs including programmatic consumption, reporting, and human-readable display.

Capabilities

Tree Format

Converts license data to hierarchical tree-formatted string for human-readable console output.

/**
 * Convert license data to tree-formatted string
 * @param data - License data from init() callback
 * @returns Tree-formatted string representation
 */
function asTree(data: LicenseData): string;

Usage Example:

const checker = require("license-checker");

checker.init({ start: process.cwd() }, function(err, packages) {
  const treeOutput = checker.asTree(packages);
  console.log(treeOutput);
});

Example Output:

├─ chalk@2.4.2
│  ├─ licenses: MIT
│  ├─ repository: https://github.com/chalk/chalk
│  └─ publisher: Sindre Sorhus
├─ debug@3.2.7
│  ├─ licenses: MIT  
│  ├─ repository: https://github.com/visionmedia/debug
│  └─ publisher: TJ Holowaychuk
└─ nopt@4.0.3
   ├─ licenses: ISC
   ├─ repository: https://github.com/npm/nopt
   └─ publisher: Isaac Z. Schlueter

Console Print

Directly prints license data in tree format to console.

/**
 * Print license data in tree format to console
 * @param data - License data from init() callback
 */
function print(data: LicenseData): void;

Usage Example:

checker.init({ start: process.cwd() }, function(err, packages) {
  checker.print(packages); // Outputs directly to console
});

Summary Format

Generates a summary showing license usage statistics with counts.

/**
 * Convert license data to summary format showing license counts
 * @param data - License data from init() callback
 * @returns Summary string with license usage statistics
 */
function asSummary(data: LicenseData): string;

Usage Example:

checker.init({ start: process.cwd() }, function(err, packages) {
  const summary = checker.asSummary(packages);
  console.log(summary);
});

Example Output:

├─ MIT: 45
├─ ISC: 12
├─ Apache-2.0: 8
├─ BSD-3-Clause: 5
├─ BSD-2-Clause: 3
└─ GPL-3.0: 1

CSV Format

Exports license data as comma-separated values for spreadsheet import and data analysis.

/**
 * Convert license data to CSV format
 * @param data - License data from init() callback
 * @param customFormat - Optional custom field specification
 * @param csvComponentPrefix - Optional prefix for component column
 * @returns CSV-formatted string
 */
function asCSV(data: LicenseData, customFormat?: CustomFormat, csvComponentPrefix?: string): string;

interface CustomFormat {
  [fieldName: string]: string | boolean;
}

Usage Examples:

// Basic CSV output
const csvOutput = checker.asCSV(packages);
console.log(csvOutput);

// CSV with custom format
const customCsv = checker.asCSV(packages, {
  "name": "",
  "version": "", 
  "licenses": "",
  "repository": "",
  "publisher": ""
});

// CSV with component prefix
const prefixedCsv = checker.asCSV(packages, customFormat, "my-app");

Example Output (basic):

"module name","license","repository"
"chalk@2.4.2","MIT","https://github.com/chalk/chalk"
"debug@3.2.7","MIT","https://github.com/visionmedia/debug"
"nopt@4.0.3","ISC","https://github.com/npm/nopt"

Example Output (with custom format):

"module name","name","version","licenses","repository","publisher"
"chalk@2.4.2","chalk","2.4.2","MIT","https://github.com/chalk/chalk","Sindre Sorhus"
"debug@3.2.7","debug","3.2.7","MIT","https://github.com/visionmedia/debug","TJ Holowaychuk"

Example Output (with component prefix):

"component","module name","license","repository"
"my-app","chalk@2.4.2","MIT","https://github.com/chalk/chalk"
"my-app","debug@3.2.7","MIT","https://github.com/visionmedia/debug"

Markdown Format

Converts license data to markdown format for documentation and reports.

/**
 * Convert license data to markdown format
 * @param data - License data from init() callback  
 * @param customFormat - Optional custom field specification
 * @returns Markdown-formatted string
 */
function asMarkDown(data: LicenseData, customFormat?: CustomFormat): string;

Usage Examples:

// Basic markdown output
const mdOutput = checker.asMarkDown(packages);
console.log(mdOutput);

// Markdown with custom format
const customMd = checker.asMarkDown(packages, {
  "licenses": "",
  "publisher": "",
  "description": ""
});

Example Output (basic):

[chalk@2.4.2](https://github.com/chalk/chalk) - MIT
[debug@3.2.7](https://github.com/visionmedia/debug) - MIT  
[nopt@4.0.3](https://github.com/npm/nopt) - ISC

Example Output (with custom format):

- **[chalk@2.4.2](https://github.com/chalk/chalk)**
    - licenses: MIT
    - publisher: Sindre Sorhus
    - description: Terminal string styling done right
 - **[debug@3.2.7](https://github.com/visionmedia/debug)**
    - licenses: MIT
    - publisher: TJ Holowaychuk
    - description: small debugging utility

Custom Format Specification

The customFormat parameter allows controlling which fields are included in CSV and Markdown output:

interface CustomFormat {
  [fieldName: string]: string | boolean;
}

Field Options:

String values: Use as default if field missing from package data
Boolean false: Exclude field from output entirely
Empty string "": Include field if present in package, empty if missing
Custom default: Use custom value if field missing

Available Fields:

name - Package name
version - Package version
licenses - License identifier(s)
repository - Repository URL
publisher - Author/publisher name
email - Author email
url - Author/package URL
path - Package filesystem path
licenseFile - License file path
licenseText - Full license text content
copyright - Copyright information
description - Package description
homepage - Package homepage URL
keywords - Package keywords array
Any other field from package.json

Custom Format Example:

const customFormat = {
  "name": "",                    // Include package name
  "version": "",                 // Include version
  "licenses": "",               // Include licenses
  "repository": "",             // Include repository
  "description": "No description", // Default value if missing
  "licenseText": false,         // Exclude license text
  "private": false,             // Exclude private flag
  "customField": "N/A"          // Custom default for missing field
};

checker.init({
  start: process.cwd(),
  customFormat: customFormat
}, function(err, packages) {
  const csv = checker.asCSV(packages, customFormat);
  const md = checker.asMarkDown(packages, customFormat);
});

CLI Integration

All formatting functions integrate with the CLI tool through command-line flags:

# Tree format (default)
license-checker

# JSON format  
license-checker --json

# CSV format
license-checker --csv

# Markdown format
license-checker --markdown

# Summary format
license-checker --summary

# Custom format from file
license-checker --customPath ./custom-format.json

# Output to file
license-checker --json --out licenses.json
license-checker --csv --out licenses.csv

The CLI automatically applies appropriate formatting based on flags and handles file output, colored terminal display, and format-specific options like CSV component prefixes.