README.md



babel-generator


Turns an AST into code.


Install

npm install --save-dev babel-generator


Usage

import {parse} from 'babylon';
import generate from 'babel-generator';

const code = 'class Example {}';
const ast = parse(code);

const output = generate(ast, { /* options */ }, code);


Options

Options for formatting output:


name
type
default
description


auxiliaryCommentBefore
string

Optional string to add as a block comment at the start of the output file


auxiliaryCommentAfter
string

Optional string to add as a block comment at the end of the output file


shouldPrintComment
function
opts.comments
Function that takes a comment (as a string) and returns true if the comment should be included in the output.  By default, comments are included if opts.comments is true or if opts.minifed is false and the comment contains @preserve or @license


retainLines
boolean
false
Attempt to use the same line numbers in the output code as in the source code (helps preserve stack traces)


retainFunctionParens
boolean
false
Retain parens around function expressions (could be used to change engine parsing behavior)


comments
boolean
true
Should comments be included in output


compact
boolean or 'auto'

opts.minified
Set to true to avoid adding whitespace for formatting


minified
boolean
false
Should the output be minified


concise
boolean
false
Set to true to reduce whitespace (but not as much as opts.compact)


quotes

'single' or 'double'

autodetect based on ast.tokens

The type of quote to use in the output


filename
string

Used in warning messages


flowCommaSeparator
boolean
false
Set to true to use commas instead of semicolons as Flow property separators


jsonCompatibleStrings
boolean
false
Set to true to run jsesc with "json": true to print "\u00A9" vs. "©";


Options for source maps:


name
type
default
description


sourceMaps
boolean
false
Enable generating source maps


sourceMapTarget
string

The filename of the generated code that the source map will be associated with


sourceRoot
string

A root for all relative URLs in the source map


sourceFileName
string

The filename for the source code (i.e. the code in the code argument).  This will only be used if code is a string.


AST from Multiple Sources

In most cases, Babel does a 1:1 transformation of input-file to output-file.  However,
you may be dealing with AST constructed from multiple sources - JS files, templates, etc.
If this is the case, and you want the sourcemaps to reflect the correct sources, you'll need
to pass an object to generate as the code parameter.  Keys
should be the source filenames, and values should be the source content.

Here's an example of what that might look like:

import {parse} from 'babylon';
import generate from 'babel-generator';

const a = 'var a = 1;';
const b = 'var b = 2;';
const astA = parse(a, { sourceFilename: 'a.js' });
const astB = parse(b, { sourceFilename: 'b.js' });
const ast = {
  type: 'Program',
  body: [].concat(astA.program.body, astB.program.body)
};

const { code, map } = generate(ast, { sourceMaps: true }, {
  'a.js': a,
  'b.js': b
});

// Sourcemap will point to both a.js and b.js where appropriate.