burrito
Burrito makes it easy to do crazy stuff with the javascript AST.
This is super useful if you want to roll your own stack traces or build a code
coverage tool.
examples
microwave
examples/microwave.js
var burrito = require('burrito');
var res = burrito.microwave('Math.sin(2)', function (node) {
if (node.name === 'num') node.wrap('Math.PI / %s');
});
console.log(res); // sin(pi / 2) == 1
output:
1
wrap
examples/wrap.js
var burrito = require('burrito');
var src = burrito('f() && g(h())\nfoo()', function (node) {
if (node.name === 'call') node.wrap('qqq(%s)');
});
console.log(src);
output:
qqq(f()) && qqq(g(qqq(h())));
qqq(foo());
methods
var burrito = require('burrito');
burrito(code, cb)
Given some source code and a function trace, walk the ast by expression.
The cb gets called with a node object described below.
If code is an Array then it is assumbed to be an AST which you can generate
yourself with burrito.parse(). The AST must be annotated, so make sure to
burrito.parse(src, false, true).
burrito.microwave(code, context={}, cb)
Like burrito() except the result is run using
vm.runInNewContext(res, context).
node object
node.name
Name is a string that contains the type of the expression as named by uglify.
node.wrap(s)
Wrap the current expression in s.
If s is a string, "%s" will be replaced with the stringified current
expression.
If s is a function, it is called with the stringified current expression and
should return a new stringified expression.
If the node.name === "binary", you get the subterms "%a" and "%b" to play with
too. These subterms are applied if s is a function too: s(expr, a, b).
Protip: to insert multiple statements you can use javascript's lesser-known block
syntax that it gets from C:
if (node.name === 'stat') node.wrap('{ foo(); %s }')
node.node
raw ast data generated by uglify
node.value
node.node.slice(1) to skip the annotations
node.start
The start location of the expression, like this:
{ type: 'name',
value: 'b',
line: 0,
col: 3,
pos: 3,
nlb: false,
comments_before: [] }
node.end
The end location of the expression, formatted the same as node.start.
node.state
The state of the traversal using traverse.
node.source()
Returns a stringified version of the expression.
node.parent()
Returns the parent node or null if the node is the root element.
node.label()
Return the label of the present node or null if there is no label.
Labels are returned for "call", "var", "defun", and "function" nodes.
Returns an array for "var" nodes since var statements can
contain multiple labels in assignment.
install
With npm you can just:
npm install burrito
in the browser
Burrito works in browser with
browserify.
It has been tested against:
- Internet Explorer 5.5, 6.0, 7.0, 8.0, 9.0
- Firefox 3.5
- Chrome 6.0
- Opera 10.6
- Safari 5.0
kudos
Heavily inspired by (and previously mostly lifted outright from) isaacs's nifty
tmp/instrument.js thingy from uglify-js.