babylon

Babylon is a JavaScript parser used in Babel.

• ES6 enabled by default.
• Comment attachment.
• Support for JSX and Flow.
• Support for experimental language proposals.

Credits

Heavily based on acorn and acorn-jsx, thanks to the awesome work of @RReverser and @marijnh.

Significant diversions are expected to occur in the future such as streaming, EBNF definitions, sweet.js integration, interspacial parsing and more.

API

babylon.parse(code, [options])

Options

• allowImportExportEverywhere: By default, import and export declarations can only appear at a program's top level. Setting this option to true allows them anywhere where a statement is allowed.

• allowReturnOutsideFunction: By default, a return statement at the top level raises an error. Set this to true to accept such code.

• allowSuperOutsideMethod TODO

• sourceType: Indicate the mode the code should be parsed in. Can be either "script" or "module".

• sourceFilename: Correlate output AST nodes with their source filename. Useful when generating code and source maps from the ASTs of multiple input files.

• plugins: Array containing the plugins that you want to enable.

Output

Babylon generates AST according to Babel AST format. It is based on ESTree spec with the following deviations:

• Literal token is replaced with StringLiteral, NumericLiteral, BooleanLiteral, NullLiteral, RegExpLiteral
• Property token is replaced with ObjectProperty and ObjectMethod
• MethodDefinition is replaced with ClassMethod
• Program and BlockStatement contain additional directives field with Directive and DirectiveLiteral
• ClassMethod, ObjectProperty, and ObjectMethod value property's properties in FunctionExpression is coerced/brought into the main method node.

AST for JSX code is based on Facebook JSX AST with the addition of one node type:

• JSXText

Example

require("babylon").parse("code", {
  // parse in strict mode and allow module declarations
  sourceType: "module",

  plugins: [
    // enable experimental async functions
    "asyncFunctions",

    // enable jsx and flow syntax
    "jsx",
    "flow"
  ]
});

Plugins

• jsx
• flow
• asyncFunctions
• classConstructorCall
• doExpressions
• trailingFunctionCommas
• objectRestSpread
• decorators
• classProperties
• exportExtensions
• exponentiationOperator
• asyncGenerators
• functionBind
• functionSent