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# babel-generator
> Turns an AST into code.
## Install
```sh
$ npm install babel-generator
```
## Usage
```js
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
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 make some changes to your code.
First, each node with a `loc` property (which indicates that node's original placement in the
source document) must also include a `loc.filename` property, set to the source filename.
Second, you should 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:
```js
import {parse} from 'babylon';
import generate from 'babel-generator';
const a = 'var a = 1;';
const b = 'var b = 2;';
const astA = parse(a, { filename: 'a.js' });
const astB = parse(b, { filename: 'b.js' });
const ast = {
type: 'Program',
body: [].concat(astA.body, ast2.body)
};
const { code, map } = generate(ast, { /* options */ }, {
'a.js': a,
'b.js': b
});
// Sourcemap will point to both a.js and b.js where appropriate.
```
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