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Transform the ast on a recursive walk.

browser support

build status

This modules uses acorn to create an AST from source code.

falafel döner



Put a function wrapper around all array literals.

var falafel = require('falafel');
var src = '(' + function () {
    var xs = [ 1, 2, [ 3, 4 ] ];
    var ys = [ 5, 6 ];
    console.dir([ xs, ys ]);
} + ')()';
var output = falafel(src, function (node) {
    if (node.type === 'ArrayExpression') {
        node.update('fn(' + node.source() + ')');


(function () {
    var xs = fn([ 1, 2, fn([ 3, 4 ]) ]);
    var ys = fn([ 5, 6 ]);
    console.dir(fn([ xs, ys ]));


var falafel = require('falafel')

falafel(src, opts={}, fn)

Transform the string source src with the function fn, returning a string-like transformed output object.

For every node in the ast, fn(node) fires. The recursive walk is a pre-traversal, so children get called before their parents.

Performing a pre-traversal makes it easier to write nested transforms since transforming parents often requires transforming all its children first.

The return value is string-like (it defines .toString() and .inspect()) so that you can call node.update() asynchronously after the function has returned and still capture the output.

Instead of passing a src you can also use opts.source.

All of the opts will be passed directly to acorn.

custom parser

You may pass in an instance of acorn to the opts as opts.parser to use that version instead of the version of acorn packaged with this library.

var acorn = require('acorn-jsx');
falafel(src, {parser: acorn, plugins: { jsx: true }}, function(node) {
  // this will parse jsx 


Aside from the regular esprima data, you can also call some inserted methods on nodes.

Aside from updating the current node, you can also reach into sub-nodes to call update functions on children from parent nodes.


Return the source for the given node, including any modifications made to children nodes.


Transform the source for the present node to the string s.

Note that in 'ForStatement' node types, there is an existing subnode called update. For those nodes all the properties are copied over onto the node.update() function.


Reference to the parent element or null at the root element.


With npm do:

npm install falafel