goja

The ast package declares types that represent a JavaScript Abstract Syntax Tree.

Warning: The parser and AST interfaces are currently works-in-progress, specifically regarding node types, and are subject to change in future versions.

To work with the JavaScript Abstract Syntax Tree (AST) in Goja, import the ast package from the following path:

import "github.com/dop251/goja/ast"

To use the lexical token definitions for JavaScript (ECMA5), import the package using the following path:

import "github.com/dop251/goja/token"

The BigInt type in Goja provides arbitrary-precision integers, following the ECMAScript specification. You can create BigInts using the BigInt() function or by converting various types (Strings, Booleans, Numbers, or Objects) into BigInt values.

Conversion Rules:

• String: Converted to BigInt. Throws SyntaxError if the string is invalid.
• Boolean: true becomes 1n, false becomes 0n.
• Number: Converted to BigInt. Throws RangeError if the number is Infinity, NaN, or a non-integer float.
• Object: Converted via its toPrimitiveNumber() method.
• Undefined/Null/Symbol/Number: Throws TypeError.

A FileSet represents a collection of source files. You can add files to a set and retrieve them or their positions using a compact Idx.

• AddFile(filename, src string) int: Adds a new file and returns its Idx.
• File(idx Idx) *File: Retrieves the File associated with the given Idx.
• Position(idx Idx) *Position: Converts an Idx into a human-readable Position.

The Expression interface is implemented by all expression nodes in the AST. An expression represents a piece of code that evaluates to a value.

type Expression interface {
	Node
	// contains filtered or unexported methods
}

The parser package uses ErrorList to collect multiple parsing errors.

• ErrorList implements the standard Go error interface via the Err() method.
• If the list is empty, Err() returns nil.
• You can add errors to the list using Add(position file.Position, msg string).
• Use Sort() to order errors by position.

The Position struct describes a specific location in the source code (filename, offset, line, and column). Use the String() method to get a formatted string representation.

Supported formats for String():

• file:line:column (Valid position with filename)
• line:column (Valid position without filename)
• file (Invalid position with filename)
• - (Invalid position without filename)

type Position struct {
	Filename string // The filename where the error occurred, if any
	Offset   int    // The src offset
	Line     int    // The line number, starting at 1
	Column   int    // The column number, starting at 1 (The character count)
}

// Example of String() output:
// "example.js:1:5"

All nodes in the Abstract Syntax Tree (AST) implement the Node interface. This interface provides methods to retrieve the character indices of the node within the source file.

• Idx0(): Returns the index of the first character belonging to the node.
• Idx1(): Returns the index of the first character immediately after the node.

type Node interface {
	Idx0() file.Idx // The index of the first character belonging to the node
	Idx1() file.Idx // The index of the first character immediately after the node
}