ast-replace

Replace each matched ast-node passing a test.

Usage

$ npm install --save ast-replace

var parse = require('esprima').parse;
var generate = require('escodegen').generate;
var replace = require('ast-replace');

//add rule to replace all `foo` assignments with `bar`.
var ast = replace(parse('foo = 1;'), {
	AssignmentExpression: {
		test: function(node){
			if (node.operator !== '=') return false;
			return node.left.name === 'foo';
		},
		replace: function(node){
			node.left.name = 'bar';
			return node;
		}
	}
});

generate(ast); //'bar = 1;'

API

replace(Node, replacement) → Node

Replace node matching criterias. Replacement object defines rules to apply replacements:

var replacement = {
	AssignmentExpression: {
		test: function (node) {
			this === replacement; //true

			//returning `undefined` means test is passed
		},
		replace: function (node) {
			this === replacement; //true

			//returning `null` replaces node
			return null;
		}
	},

	//supertype, matched after specific types
	Expression: {
		replace: function (node) {
			//returning `undefined` keeps node the same
		}
	}
}

Property	Type	Default	Description
test	Function	true	Test whether node found should be replaced. Testing function should return boolean. If omitted, every node will pass the test.
replace	Function, Node, undefined, null	null	A replacement for a matched node. Replacing function should return a new node or null. undefined is considered as no change.