morpher

Morpher
=======


JavaScript AST transformer and code generator, optimized for older engines.

Inspired by falafel (https://github.com/substack/node-falafel)
and free-falafel (https://github.com/freethenation/node-falafel),
but modified for performance in older JavaScript engines (eg. IE8.)

AST traversal is leaf-first (so child nodes are visited before their parents.)

Example
-------
``javascript
var code = 'var result = 1 + 2;';
var ast = acorn.parse(code, {ranges: true});
var transpiledCode = morpher.morph(code, ast, function (node, parent, replace, source) {
if (node.type === 'BinaryExpression') {
replace(node, 'postProcess(' + source(node) + ')');
}
});
console.log(transpiledCode); // Outputs var result = postProcess(1 + 2);
`

Use with a breadth-first callback
---------------------------------

To process parent nodes before their children, you can pass a second callback to .morph(...):
`javascript
var code = 'var result = 1 + 2; function test() { return 2 + 3; }';
var ast = acorn.parse(code, {ranges: true});
var transpiledCode = morpher.morph(code, ast, function (node, parent, replace, source) {
if (node.type === 'BinaryExpression' && node.inFunc) {
replace(node, 'postProcess(' + source(node) + ')');
}
}, function (node, parent) {
if (parent) {
node.inFunc = parent.inFunc;
}

if (node.type === 'FunctionDeclaration') {
node.inFunc = true;
}
});
console.log(transpiledCode); // Outputs var result = 1 + 2; function test() { return postProcess(2 + 3); }
``

Keeping up to date
------------------
- Follow me on Twitter for updates: https://twitter.com/@asmblah