jscodeshift Instructions

API Reference

Core API

`jscodeshift`

The main function that returns the jscodeshift instance.

Parameters: source (String)
Example:
javascript
```
const j = jscodeshift(sourceCode);
```

Node Traversal APIs

`find`

Finds nodes that match the provided type.

Parameters: type (String or Function)

Example:

javascript

const variableDeclarations = j.find(j.VariableDeclaration);

`findImportDeclarations`

Finds all ImportDeclarations optionally filtered by name.

Parameters: sourcePath (String)

Example:

javascript

const routerImports = j.findImportDeclarations("react-router-dom");

`closestScope`

Finds the closest enclosing scope of a node.

Example:

javascript

const closestScopes = j.find(j.Identifier).closestScope();

`closest`

Finds the nearest parent node that matches the specified type.

Parameters: type (String or Function)

Example:

javascript

const closestFunction = j.find(j.Identifier).closest(j.FunctionDeclaration);

`getVariableDeclarators`

Retrieves variable declarators from the current collection.

Parameters: callback (Function)

Example:

javascript

const variableDeclarators = j
  .find(j.Identifier)
  .getVariableDeclarators((path) => path.value.name);

`findVariableDeclarators`

Finds variable declarators by name.

Parameters: name (String)

Example:

javascript

const variableDeclarators = j.findVariableDeclarators("a");

`filter`

Filters nodes based on a predicate function.

Parameters: predicate (Function)

Example:

javascript

const constDeclarations = j
  .find(j.VariableDeclaration)
  .filter((path) => path.node.kind === "const");

`forEach`

Iterates over each node in the collection.

Parameters: callback (Function)

Example:

javascript

j.find(j.VariableDeclaration).forEach((path) => {
  console.log(path.node);
});

`some`

Checks if at least one element in the collection passes the test.

Parameters: callback (Function)

Example:

javascript

const hasVariableA = root
  .find(j.VariableDeclarator)
  .some((path) => path.node.id.name === "a");

`every`

Checks if all elements in the collection pass the test.

Parameters: callback (Function)

Example:

javascript

const allAreConst = root
  .find(j.VariableDeclaration)
  .every((path) => path.node.kind === "const");

`map`

Maps each node in the collection to a new value.

Parameters: callback (Function)

Example:

javascript

const variableNames = j
  .find(j.VariableDeclaration)
  .map((path) => path.node.declarations.map((decl) => decl.id.name));

`size`

Returns the number of nodes in the collection.

Example:

javascript

const numberOfNodes = j.find(j.VariableDeclaration).size();

`length`

Returns the number of elements in the collection.

Example:

javascript

const varCount = root.find(j.VariableDeclarator).length;

`nodes`

Returns the AST nodes in the collection.

Example:

javascript

const nodes = j.find(j.VariableDeclaration).nodes();

`paths`

Returns the paths of the found nodes.

Example:

javascript

const paths = j.find(j.VariableDeclaration).paths();

`getAST`

Returns the root AST node of the collection.

Example:
javascript
```
const ast = root.getAST();
```

`get`

Gets the first node in the collection.

Example:

javascript

const firstVariableDeclaration = j.find(j.VariableDeclaration).get();

`at`

Navigates to a specific path in the AST.

Parameters: index (Number)

Example:

javascript

const secondVariableDeclaration = j.find(j.VariableDeclaration).at(1);

`getTypes`

Returns the set of node types present in the collection.

Example:

javascript

const types = root.find(j.VariableDeclarator).getTypes();

`isOfType`

Checks if the node in the collection is of a specific type.

Parameters: type (String)

Example:

javascript

const isVariableDeclarator = root
  .find(j.VariableDeclarator)
  .at(0)
  .isOfType("VariableDeclarator");

Node Transformation APIs

`replaceWith`

Replaces the current node(s) with a new node.

Parameters: newNode (Node or Function)

Example:

javascript

j.find(j.Identifier).replaceWith((path) =>
  j.identifier(path.node.name.toUpperCase())
);

`insertBefore`

Inserts a node before the current node.

Parameters: newNode (Node)

Example:

javascript

j.find(j.FunctionDeclaration).insertBefore(
  j.expressionStatement(j.stringLiteral("Inserted before"))
);

`insertAfter`

Inserts a node after the current node.

Parameters: newNode (Node)

Example:

javascript

j.find(j.FunctionDeclaration).insertAfter(
  j.expressionStatement(j.stringLiteral("Inserted after"))
);

`remove`

Removes the current node(s).

Example:

javascript

j.find(j.VariableDeclaration).remove();

`renameTo`

Renames the nodes in the collection to a new name.

Parameters: newName (String)

Example:

javascript

root.find(j.Identifier, { name: "a" }).renameTo("x");

`toSource`

Converts the transformed AST back to source code.

Parameters: options (Object)

Example:

javascript

const transformedSource = j.toSource({ quote: "single" });

AST Grammar

jscodeshift provides 278 node types which are mapped to their corresponding node type in ast-types.

Common Node Types

AnyTypeAnnotation: A type annotation representing any type.
ArrayExpression: Represents an array literal.
ArrayPattern: A pattern that matches an array from a destructuring assignment.
ArrayTypeAnnotation: A type annotation for arrays.
ArrowFunctionExpression: An arrow function expression.
AssignmentExpression: Represents an assignment expression.
AssignmentPattern: A pattern that matches an assignment from a destructuring assignment.
AwaitExpression: Represents an await expression.
BigIntLiteral: A literal representing a big integer.
BinaryExpression: Represents a binary expression.
BlockStatement: Represents a block statement.
BooleanLiteral: A literal representing a boolean value.
BreakStatement: Represents a break statement.
CallExpression: Represents a call expression.
CatchClause: Represents a catch clause in a try statement.
ClassDeclaration: Represents a class declaration.
ClassExpression: Represents a class expression.
ClassMethod: Represents a method of a class.
ClassProperty: Represents a property of a class.
Comment: Represents a comment in the code.
ConditionalExpression: Represents a conditional expression (ternary).
ContinueStatement: Represents a continue statement.
DebuggerStatement: Represents a debugger statement.
Declaration: Represents a declaration in the code.
DoWhileStatement: Represents a do…while statement.
ExportAllDeclaration: Represents an export all declaration.
ExportDeclaration: Represents an export declaration.
ExportDefaultDeclaration: Represents an export default declaration.
ExportNamedDeclaration: Represents a named export declaration.
ExpressionStatement: Represents an expression statement.
File: Represents a file in the AST.
ForInStatement: Represents a for-in statement.
ForOfStatement: Represents a for-of statement.
ForStatement: Represents a for statement.
FunctionDeclaration: Represents a function declaration.
FunctionExpression: Represents a function expression.
Identifier: Represents an identifier.
IfStatement: Represents an if statement.
ImportDeclaration: Represents an import declaration.
ImportDefaultSpecifier: Represents a default import specifier.
ImportNamespaceSpecifier: Represents a namespace import specifier.
ImportSpecifier: Represents an import specifier.
InterfaceDeclaration: Represents an interface declaration.
JSXAttribute: Represents an attribute in a JSX element.
JSXElement: Represents a JSX element.
JSXExpressionContainer: Represents an expression container in JSX.
JSXFragment: Represents a JSX fragment.
JSXIdentifier: Represents an identifier in JSX.
JSXText: Represents text in JSX.
Literal: Represents a literal value.
LogicalExpression: Represents a logical expression.
MemberExpression: Represents a member expression.
MethodDefinition: Represents a method definition.
NewExpression: Represents a new expression.
ObjectExpression: Represents an object expression.
ObjectPattern: Represents an object pattern for destructuring.
ObjectProperty: Represents a property in an object.
Program: Represents the entire program.
Property: Represents a property in an object.
ReturnStatement: Represents a return statement.
SpreadElement: Represents a spread element in an array or function call.
StringLiteral: Represents a string literal.
SwitchCase: Represents a case in a switch statement.
SwitchStatement: Represents a switch statement.
TemplateLiteral: Represents a template literal.
ThisExpression: Represents the this expression.
ThrowStatement: Represents a throw statement.
TryStatement: Represents a try statement.
TSAnyKeyword: Represents the TypeScript any keyword.
TSArrayType: Represents a TypeScript array type.
TSAsExpression: Represents a TypeScript as-expression.
TSBooleanKeyword: Represents the TypeScript boolean keyword.
TSDeclareFunction: Represents a TypeScript function declaration.
TSEnumDeclaration: Represents a TypeScript enum declaration.
TSInterfaceDeclaration: Represents a TypeScript interface declaration.
TSNumberKeyword: Represents the TypeScript number keyword.
TSStringKeyword: Represents the TypeScript string keyword.
TSTypeAliasDeclaration: Represents a TypeScript type alias declaration.
TSTypeAnnotation: Represents a TypeScript type annotation.
TSTypeReference: Represents a type reference in TypeScript.
TSUnionType: Represents a union type in TypeScript.
UnaryExpression: Represents a unary expression.
VariableDeclaration: Represents a variable declaration.
VariableDeclarator: Represents a variable declarator.
WhileStatement: Represents a while statement.

For a complete list and detailed structure of each node, refer to the AST Grammar documentation.