Registry / devops / babel-plugin-define-patterns

babel-plugin-define-patterns

library1.0.0jsnpmunverified

babel-plugin-define-patterns is a Babel plugin designed to perform build-time constant and expression replacements. It operates directly on the Abstract Syntax Tree (AST) during the Babel compilation process, allowing developers to define arbitrary JavaScript expressions or patterns that are replaced with static values. This functionality is analogous to Webpack's DefinePlugin but is integrated at the Babel transformation level, making it bundler-agnostic. Key use cases include injecting environment variables (e.g., `process.env.NODE_ENV`), build-time flags (e.g., `__DEV__`), or specific build metadata (e.g., `require('currentBuildNumber')`). The current stable version is 1.0.0. As a Babel plugin, its release cadence is typically tied to Babel's ecosystem, though specific information on its own cadence is not provided. Its primary differentiator is its deep integration into the Babel AST transformation, offering fine-grained control over code alteration before bundling.

devops

npm install babel-plugin-define-patterns

github ↗package ↗

INSTALL

IMPORT

SIG · BABEL-PLUGIN-DEFIN

babel-plugin-define-patterns

devopsjavascriptv1.0.0

Install

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Import

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Disk

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Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

define-patterns

✓ ["define-patterns", { /* options */ }]

✗ ["babel-plugin-define-patterns", { /* options */ }]

The plugin is typically referenced by its short name ('define-patterns') in `babel.config.json` or similar configuration files.

pluginModule

✓ const definePatterns = require('babel-plugin-define-patterns');

✗ import definePatterns from 'babel-plugin-define-patterns';

When using a JavaScript configuration file (e.g., `babel.config.js`) or programmatically, the plugin module is loaded via CommonJS `require()`.

replacements

✓ { "plugins": [ ["define-patterns", { "replacements": { "process.env.NODE_ENV": "production" } }] ] }

The core configuration object where patterns are mapped to their replacement values.

This quickstart demonstrates how to configure `babel-plugin-define-patterns` in `babel.config.json` to replace various expressions with static values at build-time.

// Install the plugin as a dev dependency // npm install --save-dev babel-plugin-define-patterns // babel.config.json example { "plugins": [ ["define-patterns", { "replacements": { "process.env.NODE_ENV": "production", "typeof window": "object", "__DEV__": true, "require('currentBuildNumber')": 42 } }] ] } // Input file (e.g., src/app.js) // const env = process.env.NODE_ENV; // const isBrowser = typeof window === 'object'; // if (__DEV__) console.log('Development mode'); // const buildNum = require('currentBuildNumber'); // After Babel compilation with the above config, it would transform to: // const env = "production"; // const isBrowser = true; // if (true) console.log('Development mode'); // A minifier would remove the 'if' and just keep the console.log // const buildNum = 42;

Debug

Known issues

gotchaThe order of Babel plugins matters. If another plugin modifies an expression that `babel-plugin-define-patterns` is configured to replace, the pattern might not be matched, and the replacement will not occur. Ensure `define-patterns` runs before any transformations that might alter the target expressions.

fix

Adjust the order of plugins in your Babel configuration. `babel-plugin-define-patterns` should typically be placed early in the plugin array.

affects: >=1.0.0

gotchaPatterns are matched as exact string expressions within the AST. This means `process.env.NODE_ENV` will only match that exact string expression, not `process.env['NODE_ENV']` or `const myEnv = process.env; myEnv.NODE_ENV;`.

fix

Ensure the `replacements` keys exactly match the expressions as they appear in your source code's AST. For more complex scenarios, consider using `babel-plugin-macros` or a custom Babel plugin.

affects: >=1.0.0

gotchaBe mindful of replacing expressions with primitive JavaScript values (e.g., `true`, `false`, `42`) versus string literals (e.g., `'production'`, `'development'`). Replacing with `true` allows dead code elimination by minifiers (e.g., `if (true)`), while replacing with `'production'` will result in a string literal.

fix

Use boolean or numeric literals (`true`, `false`, `42`) if you intend for minifiers to perform dead-code elimination. Use string literals (`'production'`, `'development'`) if you want the string itself to be injected.

affects: >=1.0.0

gotchaOverwriting globally available identifiers like `process` or `window` via this plugin can have unintended side effects or break third-party libraries that rely on their original behavior, especially when targeting different environments.

fix

Only replace expressions that are safely isolated (e.g., specific environment variables or custom global flags). Thoroughly test your application if you are replacing core global object properties.

affects: >=1.0.0

Errors

Common errors & fixes

Error: .plugins[X] must be an array or a string

The plugin configuration is not correctly defined as an array containing the plugin name and its options.

fix

Ensure the plugin is configured as `['define-patterns', { 'replacements': { /* ... */ } }]` within your `plugins` array in `babel.config.json`.

ReferenceError: process is not defined

Attempting to use `process.env.NODE_ENV` in a browser environment without it being transformed by `babel-plugin-define-patterns` or another similar tool, or if the plugin configuration is incorrect.

fix

Verify that `babel-plugin-define-patterns` is correctly configured and running during your build process, and that `process.env.NODE_ENV` is included in its `replacements` options to be replaced with a static value.

Expression 'X' was not replaced as expected.

The string pattern defined in `replacements` does not exactly match the expression in the source code, or another Babel plugin has altered the expression before `define-patterns` could process it.

fix

Double-check the exact string match for your pattern in the `replacements` object. Review your Babel plugin order to ensure `define-patterns` runs before any plugins that might transform the target expression.

Upgrade

Version history

1.0.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/discord/babel-plugin-define-patterns ↗

packagehttps://www.npmjs.com/package/babel-plugin-define-patterns ↗