SourceCode

Represents parsed JavaScript source code

The SourceCode class represents parsed source code and provides methods for working with the AST (Abstract Syntax Tree), tokens, comments, and source text.

Constructor

const { SourceCode } = require("eslint");
const sourceCode = new SourceCode(textOrConfig, ast);

textOrConfig · string | object · required

Either the source code text or a configuration object.

Show config properties

text · string · required

The source code text.

ast · ASTNode · required

The Program node of the AST.

hasBOM · boolean

Indicates if the text has a Unicode BOM.

parserServices · object

Parser services provided by the parser.

scopeManager · ScopeManager

The scope manager for the source code.

visitorKeys · object

Visitor keys to traverse the AST.

ast · ASTNode

The Program node (when using the simple string constructor).

Properties

text

const text = sourceCode.text;

text · string

The full source code text.

ast

const ast = sourceCode.ast;

ast · ASTNode

The Program node of the Abstract Syntax Tree.

lines

const lines = sourceCode.lines;

lines · string[]

Array of lines in the source code (split by line breaks).

hasBOM

const hasBOM = sourceCode.hasBOM;

hasBOM · boolean

Whether the source code has a Unicode Byte Order Mark.

parserServices

const services = sourceCode.parserServices;

parserServices · object

Additional services provided by the parser (e.g., TypeScript type information).

scopeManager

const scopeManager = sourceCode.scopeManager;

scopeManager · ScopeManager

The scope manager containing scope analysis results.

visitorKeys

const visitorKeys = sourceCode.visitorKeys;

visitorKeys · object

Visitor keys for traversing the AST.

Methods

getText()

Gets the source code text for a node or token.

const text = sourceCode.getText(nodeOrToken, beforeCount, afterCount);

nodeOrToken · ASTNode | Token

The node or token to get text for. If omitted, returns entire source.

beforeCount · number · default: "0"

Number of characters before the node to include.

afterCount · number · default: "0"

Number of characters after the node to include.

text · string

The source code text.

getLines()

Gets the source code lines.

const lines = sourceCode.getLines();

lines · string[]

Array of source code lines.

getAllComments()

Gets all comments in the source code.

const comments = sourceCode.getAllComments();

comments · Token[]

Array of comment tokens.

getComments()

Gets comments for a specific node.

const comments = sourceCode.getComments(node);

node · ASTNode · required

The node to get comments for.

comments · object

Show properties

leading · Token[]

Comments before the node.

trailing · Token[]

Comments after the node.

getLoc()

Gets the location information for a node or token.

const loc = sourceCode.getLoc(nodeOrToken);

nodeOrToken · ASTNode | Token · required

The node or token.

loc · object

Show properties

start · object

Start position with line and column (1-based).

end · object

End position with line and column (1-based).

getRange()

Gets the range for a node or token.

const range = sourceCode.getRange(nodeOrToken);

nodeOrToken · ASTNode | Token · required

The node or token.

range · [number, number]

The [start, end] character indices (0-based).

getTokens()

Gets tokens for a node.

const tokens = sourceCode.getTokens(node, beforeCount, afterCount);

node · ASTNode · required

The node to get tokens for.

beforeCount · number · default: "0"

Number of tokens before the node to include.

afterCount · number · default: "0"

Number of tokens after the node to include.

tokens · Token[]

Array of tokens.

getFirstToken()

Gets the first token of a node.

const token = sourceCode.getFirstToken(node, options);

node · ASTNode · required

The node.

options · number | function | object

Skip count, filter function, or options object.

token · Token | null

The first token, or null if not found.

getLastToken()

Gets the last token of a node.

const token = sourceCode.getLastToken(node, options);

node · ASTNode · required

The node.

options · number | function | object

Skip count, filter function, or options object.

token · Token | null

The last token, or null if not found.

getTokenBefore()

Gets the token before a node or token.

const token = sourceCode.getTokenBefore(nodeOrToken, options);

nodeOrToken · ASTNode | Token · required

The node or token.

options · number | function | object

Skip count, filter function, or options object.

token · Token | null

The previous token, or null if not found.

getTokenAfter()

Gets the token after a node or token.

const token = sourceCode.getTokenAfter(nodeOrToken, options);

nodeOrToken · ASTNode | Token · required

The node or token.

options · number | function | object

Skip count, filter function, or options object.

token · Token | null

The next token, or null if not found.

getFirstTokenBetween()

Gets the first token between two nodes or tokens.

const token = sourceCode.getFirstTokenBetween(left, right, options);

left · ASTNode | Token · required

The left node or token.

right · ASTNode | Token · required

The right node or token.

options · number | function | object

Skip count, filter function, or options object.

token · Token | null

The first token between, or null if not found.

getTokensBetween()

Gets all tokens between two nodes or tokens.

const tokens = sourceCode.getTokensBetween(left, right, padding);

left · ASTNode | Token · required

The left node or token.

right · ASTNode | Token · required

The right node or token.

padding · number · default: "0"

Number of extra tokens to include on each side.

tokens · Token[]

Array of tokens between the two nodes/tokens.

getTokenByRangeStart()

Gets a token by its range start position.

const token = sourceCode.getTokenByRangeStart(index, options);

index · number · required

The range start index.

options · object

Options for the search.

token · Token | null

The token at that position, or null.

getNodeByRangeIndex()

Gets the deepest node containing a given index.

const node = sourceCode.getNodeByRangeIndex(index);

index · number · required

The character index.

node · ASTNode | null

The deepest node containing the index, or null.

isSpaceBetween()

Checks if there is whitespace between two nodes or tokens.

const hasSpace = sourceCode.isSpaceBetween(first, second);

first · ASTNode | Token · required

The first node or token.

second · ASTNode | Token · required

The second node or token.

hasSpace · boolean

True if there is whitespace between them.

getScope()

Gets the scope for a node.

const scope = sourceCode.getScope(node);

node · ASTNode · required

The node to get the scope for.

scope · Scope

The scope object.

markVariableAsUsed()

Marks a variable as used in a specific scope.

const found = sourceCode.markVariableAsUsed(name, node);

name · string · required

The variable name.

node · ASTNode

The node to start the search from.

found · boolean

True if the variable was found and marked.

getAncestors()

Gets the ancestor nodes of a given node.

const ancestors = sourceCode.getAncestors(node);

node · ASTNode · required

The node.

ancestors · ASTNode[]

Array of ancestor nodes from closest to farthest.

getDeclaredVariables()

Gets variables declared by a node.

const variables = sourceCode.getDeclaredVariables(node);

node · ASTNode · required

The node.

variables · Variable[]

Array of declared variables.

Examples

Getting Text

const { SourceCode } = require("eslint");

// Assuming you have an AST node
const text = sourceCode.getText(node);
console.log(text);

// Get text with surrounding context
const textWithContext = sourceCode.getText(node, 2, 2);
console.log(textWithContext);

Working with Tokens

// Get all tokens for a node
const tokens = sourceCode.getTokens(node);

// Get first and last tokens
const first = sourceCode.getFirstToken(node);
const last = sourceCode.getLastToken(node);

// Get tokens between two nodes
const between = sourceCode.getTokensBetween(leftNode, rightNode);

console.log(tokens, first, last, between);

Checking Spacing

// Check if there's whitespace between tokens
const hasSpace = sourceCode.isSpaceBetween(token1, token2);

if (!hasSpace) {
  context.report({
    node,
    message: "Expected space between tokens."
  });
}

Scope Analysis

// Get the scope for a node
const scope = sourceCode.getScope(node);

// Get declared variables
const variables = sourceCode.getDeclaredVariables(node);

// Mark a variable as used
sourceCode.markVariableAsUsed("myVar", node);

console.log(scope, variables);

Usage in Rules

The SourceCode object is available in rules through the context object:

module.exports = {
  create(context) {
    const sourceCode = context.sourceCode;

    return {
      Identifier(node) {
        const text = sourceCode.getText(node);
        const token = sourceCode.getFirstToken(node);
        
        // Your rule logic here
      }
    };
  }
};