simple but flexible AST traversal with pre and post visitors
npm install ast-traversejavascript
// ast is a Mozilla Parser API compatible structure
// generated by Esprima or another parser
var ast = require("esprima").parse("f(1, x) + 2");var traverse = require("ast-traverse");
// print AST node types, pre-order (node first, then its children)
traverse(ast, {pre: function(node, parent, prop, idx) {
console.log(node.type + (parent ? " from parent " + parent.type +
" via " + prop + (idx !== undefined ? "[" + idx + "]" : "") : ""));
}});
console.log();
/*
=>
Program
ExpressionStatement from parent Program via body[0]
BinaryExpression from parent ExpressionStatement via expression
CallExpression from parent BinaryExpression via left
Identifier from parent CallExpression via callee
Literal from parent CallExpression via arguments[0]
Identifier from parent CallExpression via arguments[1]
Literal from parent BinaryExpression via right
*/
// you can also visit post-order, or both
// all four arguments are provided to both visitors (left out unused below)
var indent = 0;
traverse(ast, {
pre: function(node) {
console.log(Array(indent + 1).join(" ") + node.type);
indent += 4;
},
post: function() {
indent -= 4;
}
});
console.log();
/*
=>
Program
ExpressionStatement
BinaryExpression
CallExpression
Identifier
Literal
Identifier
Literal
*/
// return false from the pre-visitor to skip traversing its children
// throw an exception to abort traversal
// by default node property names beginning with $ are skipped
// but you can supply your own skipProperty function instead
traverse(ast, {
pre: function(node) {
console.log(node.type);
},
skipProperty: function(prop, node) {
return prop === "parent" || prop === "expression";
}
});
/*
=>
Program
ExpressionStatement
*/
`Installation
$3
Install using npm npm install ast-traverse
javascript
var traverse = require("ast-traverse");
`$3
Clone the repo and include it in a script tag git clone https://github.com/olov/ast-traverse.git
html
``