falafel
Transform the ast on a recursive walk.
This module is like burrito, except that it uses esprima instead of uglify for friendlier-looking ast nodes.
example
array.js
Put a function wrapper around all array literals.
var falafel = ;var src = '(' + {var xs = 1 2 3 4 ;var ys = 5 6 ;consoledir xs ys ;} + ')()';var output =;console;
output:
(function () {
var xs = fn([ 1, 2, fn([ 3, 4 ]) ]);
var ys = fn([ 5, 6 ]);
console.dir(fn([ xs, ys ]));
})()
custom keyword
Creating custom keywords is super simple!
This example creates a new beep
keyword that uppercases its arguments:
var falafel = ;var src = 'console.log(beep "boop", "BOOP");';{if id === 'beep' return true;}var output =;console;
Now the source string console.log(beep "boop", "BOOP");
is converted to:
$ node example/keyword.js
console.log(String("boop").toUpperCase(), "BOOP");
which we can execute:
$ node example/keyword.js | node
BOOP BOOP
Neat!
methods
var 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 esprima except for 'range'
which
is always turned on because falafel needs it.
Some of the options you might want from esprima includes:
'loc'
, 'raw'
, 'comment'
, 'tokens'
, and 'tolerant'
.
falafel uses a custom patch of esprima with support for an opts.isKeyword()
function. When opts.isKeyword(id)
returns true
, the string id
will be
treated as a keyword. You can use this behavior to create custom unary
expression keywords.
An opts.isKeyword(id)
value that is a string will be mapped to existing types.
The only currently supported string value is "block"
.
nodes
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.
node.source()
Return the source for the given node, including any modifications made to children nodes.
node.update(s)
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.
node.parent
Reference to the parent element or null
at the root element.
install
With npm do:
npm install falafel
license
MIT