babel-preset-es2015

babel-preset-es2015 is a comprehensive Babel preset that provides a complete collection of transformation plugins for converting ES2015 (ES6) JavaScript features to ES5-compatible code. It includes 24 individual transformation plugins covering all ES2015 language features like arrow functions, classes, destructuring, template literals, modules, and more.

Deprecation Notice: This package has been deprecated since Babel 7.0.0 in favor of @babel/preset-env, which provides more intelligent targeting based on supported environments rather than language version.

Package Information

• Package Name: babel-preset-es2015
• Package Type: npm
• Language: JavaScript
• Installation: npm install --save-dev babel-preset-es2015

Core Imports

This preset is typically used via Babel configuration files rather than direct imports:

.babelrc

{
  "presets": ["es2015"]
}

babel.config.js

module.exports = {
  presets: ["es2015"]
};

For direct imports (advanced usage):

const es2015 = require("babel-preset-es2015");

Basic Usage

Configuration File Usage (.babelrc)

{
  "presets": ["es2015"]
}

With Options

{
  "presets": [
    ["es2015", {
      "loose": true,
      "modules": false,
      "spec": true
    }]
  ]
}

Programmatic Usage with babel-core

const babel = require("babel-core");

// Using preset by name (most common)
const result = babel.transform(code, {
  presets: ["es2015"]
});

// Using with options
const resultWithOptions = babel.transform(code, {
  presets: [["es2015", { loose: true, modules: "amd" }]]
});

// Direct preset import (advanced)
const es2015 = require("babel-preset-es2015");
const directResult = babel.transform(code, {
  presets: [es2015]
});

Architecture

babel-preset-es2015 follows Babel's preset architecture:

• Static Configuration: Default export provides pre-configured plugin array
• Dynamic Configuration: buildPreset function creates customized configurations
• Plugin Orchestration: Bundles 24 ES2015 transformation plugins in correct execution order
• Backward Compatibility: Dual export strategy supports both old and new Babel versions

Capabilities

Default Preset Configuration

The main export is a preset configuration object with default ES2015 transformation settings.

// Default export - preset configuration object with buildPreset property
interface PresetConfig {
  plugins: Array<PluginConfiguration>;
  buildPreset?: (context: any, options?: PresetOptions) => { plugins: Array<PluginConfiguration> };
}

Usage:

const es2015 = require("babel-preset-es2015");
console.log(es2015.plugins); // Array of plugin configurations
console.log(typeof es2015.buildPreset); // "function"

Custom Preset Builder

The preset object has a buildPreset property function for creating customized configurations.

/**
 * Property function on the default export for creating customized preset configurations
 * @param context - Babel context object (typically null)
 * @param options - Configuration options
 * @returns Preset configuration object with plugins array
 */
preset.buildPreset(
  context: any,
  options?: PresetOptions
): { plugins: Array<PluginConfiguration> };

interface PresetOptions {
  /** Enable loose transformations for faster, less spec-compliant output */
  loose?: boolean;
  /** Module transformation type or false to disable module transforms */
  modules?: "commonjs" | "amd" | "umd" | "systemjs" | false;
  /** Enable spec-compliant transformations for more accurate ES2015 behavior */
  spec?: boolean;
}

Usage:

const es2015 = require("babel-preset-es2015");

// Create custom preset using buildPreset property
const customPreset = es2015.buildPreset(null, {
  loose: true,
  modules: "amd",
  spec: false
});

// Use in Babel configuration
const babel = require("babel-core");
const result = babel.transform(code, {
  presets: [customPreset]
});

Option: loose

Controls the transformation style for plugins that support loose mode.

interface LooseOption {
  /** When true, enables faster but less spec-compliant transformations */
  loose: boolean; // default: false
}

Effect: Loose mode produces simpler, faster code but may not handle all edge cases according to ES2015 specification.

Examples:

• Classes: Uses simple constructor functions instead of complex inheritance helpers
• Template literals: Uses string concatenation instead of tagged template helpers
• Destructuring: Uses simpler variable assignments where possible

Option: modules

Controls ES6 module transformation to different module systems.

interface ModulesOption {
  /** Target module system or false to preserve ES6 modules */
  modules: "commonjs" | "amd" | "umd" | "systemjs" | false; // default: "commonjs"
}

Module Types:

• "commonjs": Node.js style require()/module.exports
• "amd": Asynchronous Module Definition for RequireJS
• "umd": Universal Module Definition for browsers and Node.js
• "systemjs": SystemJS dynamic module loader format
• false: Preserve ES6 import/export statements

Option: spec

Controls whether to use spec-compliant transformations.

interface SpecOption {
  /** When true, uses more spec-compliant but potentially slower transformations */
  spec: boolean; // default: false
}

Effect: Spec mode produces code that more closely follows ES2015 specification behavior, but may be larger and slower.

Error Handling

The preset validates options and throws descriptive errors for invalid configurations:

// Thrown for invalid loose option
throw new Error("Preset es2015 'loose' option must be a boolean.");

// Thrown for invalid spec option  
throw new Error("Preset es2015 'spec' option must be a boolean.");

// Thrown for invalid modules option
throw new Error(
  "Preset es2015 'modules' option must be 'false' to indicate no modules\n" +
  "or a module type which be be one of: 'commonjs' (default), 'amd', 'umd', 'systemjs'"
);

Plugin Collection

The preset includes these 24 ES2015 transformation plugins in execution order:

Core Language Features

• babel-plugin-transform-es2015-template-literals: Template string literals
• babel-plugin-transform-es2015-literals: Numeric and string literal improvements
• babel-plugin-transform-es2015-function-name: Function name inference
• babel-plugin-transform-es2015-arrow-functions: Arrow function syntax
• babel-plugin-transform-es2015-block-scoped-functions: Block-scoped function declarations
• babel-plugin-transform-es2015-classes: Class declarations and expressions
• babel-plugin-transform-es2015-object-super: Super calls in object methods
• babel-plugin-transform-es2015-shorthand-properties: Object shorthand properties
• babel-plugin-transform-es2015-duplicate-keys: Duplicate object key handling
• babel-plugin-transform-es2015-computed-properties: Computed property names
• babel-plugin-transform-es2015-for-of: For-of loop iteration
• babel-plugin-transform-es2015-sticky-regex: Sticky (y) regex flag
• babel-plugin-transform-es2015-unicode-regex: Unicode (u) regex flag
• babel-plugin-check-es2015-constants: Const declaration validation
• babel-plugin-transform-es2015-spread: Spread operator
• babel-plugin-transform-es2015-parameters: Default and rest parameters
• babel-plugin-transform-es2015-destructuring: Destructuring assignments
• babel-plugin-transform-es2015-block-scoping: Let and const declarations
• babel-plugin-transform-es2015-typeof-symbol: Typeof operator with symbols

Module Systems

• babel-plugin-transform-es2015-modules-commonjs: CommonJS modules
• babel-plugin-transform-es2015-modules-systemjs: SystemJS modules
• babel-plugin-transform-es2015-modules-amd: AMD modules
• babel-plugin-transform-es2015-modules-umd: UMD modules

Advanced Features

• babel-plugin-transform-regenerator: Generator functions (configured with async: false, asyncGenerators: false)

Types

interface PluginConfiguration {
  /** Plugin function or [plugin, options] array */
  0: Function | [Function, object];
}

interface PresetExport {
  /** Array of Babel plugin configurations */
  plugins: Array<PluginConfiguration>;
  /** Property function to create custom preset configurations (non-enumerable) */
  buildPreset?: (context: any, options?: PresetOptions) => { plugins: Array<PluginConfiguration> };
}