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Babylon is a JavaScript parser used in Babel.
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, interspatial parsing and more.
babylon.parse(code, [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.
Babylon generates AST according to Babel AST format. It is based on ESTree spec with the following deviations:
directives
field with Directive and DirectiveLiteralAST for JSX code is based on Facebook JSX AST with the addition of one node type:
JSXText
Babylon follows semver in most situations. The only thing to note is that some spec-compliancy bug fixes may be released under patch versions.
For example: We push a fix to early error on something like multiple default exports per file. That would be considered a bug fix even though it would cause a build to fail.
require("babylon").parse("code", {
// parse in strict mode and allow module declarations
sourceType: "module",
plugins: [
// enable jsx and flow syntax
"jsx",
"flow"
]
});
jsx
flow
doExpressions
objectRestSpread
decorators
classProperties
exportExtensions
asyncGenerators
functionBind
functionSent
6.10.0 (2016-09-19)
We plan to include some spec compliancy bugs in patch versions. An example was the multiple default exports issue.
It is a Syntax Error if ContainsUseStrict of FunctionBody is true and IsSimpleParameterList of FormalParameters is false. https://tc39.github.io/ecma262/2016/#sec-function-definitions-static-semantics-early-errors
More Context: tc39-notes
For example:
// this errors because it uses destructuring and default parameters
// in a function with a "use strict" directive
function a([ option1, option2 ] = []) {
"use strict";
}
The solution would be to use a top level "use strict" or to remove the destructuring or default parameters when using a function + "use strict" or to.
Added to flow in https://github.com/facebook/flow/commit/c710c40aa2a115435098d6c0dfeaadb023cd39b8
Looks like:
var a : {| x: number, y: string |} = { x: 0, y: 'foo' };
typeParameter
location in ArrowFunctionExpression
(#126) (Daniel Tschinder)FAQs
A JavaScript parser
The npm package babylon receives a total of 2,904,752 weekly downloads. As such, babylon popularity was classified as popular.
We found that babylon demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 5 open source maintainers collaborating on the project.
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