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123 lines
2.9 KiB
Markdown
123 lines
2.9 KiB
Markdown
# falafel
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Transform the [ast](http://en.wikipedia.org/wiki/Abstract_syntax_tree) on a
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recursive walk.
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[](http://ci.testling.com/substack/node-falafel)
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[](https://github.com/substack/node-falafel/actions)
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This modules uses [acorn](https://npmjs.org/package/acorn) to create an AST from
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source code.
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# example
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## array.js
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Put a function wrapper around all array literals.
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``` js
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var falafel = require('falafel');
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var src = '(' + function () {
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var xs = [ 1, 2, [ 3, 4 ] ];
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var ys = [ 5, 6 ];
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console.dir([ xs, ys ]);
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} + ')()';
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var output = falafel(src, function (node) {
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if (node.type === 'ArrayExpression') {
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node.update('fn(' + node.source() + ')');
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}
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});
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console.log(output);
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```
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output:
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```
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(function () {
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var xs = fn([ 1, 2, fn([ 3, 4 ]) ]);
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var ys = fn([ 5, 6 ]);
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console.dir(fn([ xs, ys ]));
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})()
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```
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# methods
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``` js
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var falafel = require('falafel')
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```
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## falafel(src, opts={}, fn)
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Transform the string source `src` with the function `fn`, returning a
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string-like transformed output object.
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For every node in the ast, `fn(node)` fires. The recursive walk is a
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post-order traversal, so children get called before their parents.
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Performing a post-order traversal makes it easier to write nested transforms since
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transforming parents often requires transforming all its children first.
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The return value is string-like (it defines `.toString()` and `.inspect()`) so
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that you can call `node.update()` asynchronously after the function has
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returned and still capture the output.
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Instead of passing a `src` you can also use `opts.source`.
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All of the `opts` will be passed directly to
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[acorn](https://npmjs.org/package/acorn).
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## custom parser
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You may pass in an instance of acorn to the opts as `opts.parser` to use that
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version instead of the version of acorn packaged with this library.
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```js
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var acorn = require('acorn-jsx');
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falafel(src, {parser: acorn, plugins: { jsx: true }}, function(node) {
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// this will parse jsx
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});
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```
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# nodes
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Aside from the regular [acorn](https://npmjs.org/package/acorn) data, you can also call
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some inserted methods on nodes.
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Aside from updating the current node, you can also reach into sub-nodes to call
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update functions on children from parent nodes.
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## node.source()
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Return the source for the given node, including any modifications made to
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children nodes.
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## node.update(s)
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Transform the source for the present node to the string `s`.
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Note that in `'ForStatement'` node types, there is an existing subnode called
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`update`. For those nodes all the properties are copied over onto the
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`node.update()` function.
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## node.parent
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Reference to the parent element or `null` at the root element.
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# install
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With [npm](http://npmjs.org) do:
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```
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npm install falafel
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```
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# license
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MIT
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