Node-Flags

A flexible and easy-to-use command-line flag parsing library for Node.js applications.

• Define flags across multiple files
• Support for various data types (string, boolean, integer, number, string list, multi-string)
• Easy-to-use API for defining and accessing flags
• Customizable flag validation
• Built-in help text generation

Install using your favorite package manager:

npm install flags
# or
yarn add flags
# or
pnpm add flags

Here's a quick example of how to use Node-Flags:

import * as flags from "flags";

// Define flags
flags.defineString("name", "Anonymous", "Your name");
flags.defineInteger("age", 21, "Your age in years");
flags.defineNumber("height", 1.8, "Your height in meters");
flags.defineStringList("pets", [], "List of your pets");
flags.defineMultiString("hobby", [], "Your hobbies");

// Parse command-line arguments
flags.parse();

// Access flag values
const info = [
  `Name: ${flags.get("name")}`,
  `Age: ${flags.get("age")}`,
  `Height: ${flags.get("height")}m`,
  `Pets: ${flags.get("pets").join(", ")}`,
  `Hobbies:\n  ${flags.get("hobby").join("\n  ")}`,
];

console.log(info.join("\n"));

Run your script with flags:

node example.js --name="John Doe" --age=30 --height=1.75 --pets=dog,cat --hobby=reading --hobby=gaming

Node-Flags provides several methods to define flags:

• defineString(name, defaultValue, description)
• defineBoolean(name, defaultValue, description)
• defineInteger(name, defaultValue, description)
• defineNumber(name, defaultValue, description)
• defineStringList(name, defaultValue, description)
• defineMultiString(name, defaultValue, description)

Each method returns a Flag object that allows further configuration:

flags
  .defineString("api-key")
  .setDefault("your-default-key")
  .setDescription("API key for authentication")
  .setValidator((value) => {
    if (value.length < 10) {
      throw new Error("API key must be at least 10 characters long");
    }
  })
  .setSecret(true);

• Use double dashes for flag names: --flagname
• Separate values with an equal sign or space: --flagname=value or --flagname value
• Quote complex string values: --message="Hello, World!"
• Use -- to separate flags from additional arguments: --flag1 value1 -- arg1 arg2

Access flag values using flags.get(flagName) or flags.FLAGS.flagName.get().

Flag objects also provide properties like name, defaultValue, currentValue, and isSet.

Node-Flags automatically generates help text. Access it by running your script with the --help flag.

For testing, you can pass predefined arguments to flags.parse():

flags.parse(["--flag1", "--noflag2", "--flag3=value"]);

Reset flags between test cases:

flags.reset();

This project is licensed under the MIT License. See the LICENSE file for details.