If you are upgrading from an older version, please note that version 3 ships with numerous breaking changes to the public API because virtually all areas of the library have been revised.<br />Documentation of the previous major version is available here.
Esprima .NET (BSD license) is a .NET port of the esprima.org project.
It is a standard-compliant ECMAScript
parser (also popularly known as
JavaScript).
var parser = new JavaScriptParser();
var program = parser.ParseScript("const answer = 42");
You can control the behavior of the parser by initializing and passing a ParserOptions to the parser's constructor. (For the available options, see the XML documentation of the ParserOptions class.)
Instead of ParseScript, you may use ParseModule or ParseExpression to make the parser treat the input as an ES6 module or as a plain JavaScript expression respectively.
In case the input is syntactically correct, each of these methods returns the root node of the resulting abstract syntax tree (AST), which you can freely analyze or transform. The library provides the AstVisitor and AstRewriter visitor classes to help you with such tasks.
When the input contains a severe syntax error, a ParserException is thrown. By catching it you can get details about the error. There are syntax errors though which can be tolerated by the parser. Such errors are ignored by default. You can record them by setting ParserOptions.ErrorHandler to an instance of CollectingErrorHandler. Alternatively, you can set ParserOptions.Tolerant to false to make the parser throw exceptions also in the case of tolerable syntax errors.
The library is able to write the AST (except for comments) back to JavaScript code:
var code = program.ToJavaScriptString(format: true);
It is also possible to serialize the AST into a JSON representation:
var astJson = program.ToJsonString(indent: " ");
Considering the example above this call will return the following JSON:
Here is a list of common JavaScript libraries and the time it takes to parse them,
compared to the time it took for the same script using the original Esprima in Chrome.
