Estools provides a set of utility functions to traverse, filter and map esprima ASTs.

npm install estools --save

var estools = require('estools')

Traverses all tree nodes of an AST and calls visitor functions passing the AST node.

ast is the result of esprima.parse, visitor may be a function or a visitor object.

The visitor object may define the following functions

Called when entering a node. The current node and parent node are passed as parameter

Example

traverse(ast, {
  enter : function(node, parent) {
    console.log(node.type);  // Print the node type to std out
  }
});

Called when leaving a node. The current node and parent node are passed as parameter

Example

traverse(ast, {
  leave : function(node, parent) {
    console.log(node.type);  // Print the node type to std out
  }
});

Called after enter and before leave. The current node and a parent node are passed as parameter. Additionally a function next is passed. The visit function is responsible to call next to visit child nodes. To skip child nodes just omit the call to visit.

Example

traverse(ast, {
  visit : function(node, parent, next) {
    next();
  }
});

Example skipping nodes traverse(ast, { visit : function(node, parent, next) { if (node.type != 'FunctionExpression') { // Skip child nodes of function expressions next(); } } });

Filters AST nodes and returns matching AST nodes as a flat list.

Maps ASTs and nodes to a normalized tree with node having child nodes stored in a nodes field array.