README.md
# jsstana
> s-expression match patterns for [Mozilla Parser AST](https://developer.mozilla.org/en-US/docs/SpiderMonkey/Parser_API)
[jsstana](oleg.fi/jsstana) will help you to find exactly the code snippet you are searching for.
It's much more precise than using grep.
[](http://travis-ci.org/phadej/jsstana)
[](http://badge.fury.io/js/jsstana)
## Synopsis
```javascript
var jsstana = require("jsstana");
var esprima = require("esprima");
var contents = // ...
var syntax = esprima.parse(contents);
jsstana.traverse(syntax, function (node) {
var m = jsstana.match("(call alert ?argument)", node);
if (m) {
console.log("alert called with argument", m.argument);
}
});
```
## jsgrep
The jsgrep example utility is provided
```bash
# find assertArguments calls with 4 arguments
% jsgrep '(call ?.assertArguments ? ? ? ?)' lib
matchers/literal.js:25: this.assertArguments("true/false/null/infinity/nan/undefined", 0, arguments, 1);
matchers/literal.js:111: this.assertArguments("literal", 1, arguments, 1);
matchers/member.js:18: that.assertArguments("member/property/subscript", 2, arguments, 1);
matchers/operator.js:63: that.assertArguments(ratorName, 3, arguments, 3);
matchers/operator.js:98: that.assertArguments("unary", 2, arguments, 1);
matchers/operator.js:128: that.assertArguments("update/postfix/prefix", 2, arguments, 1);
matchers/simple.js:7: this.assertArguments(rator, 1, arguments, 3);
```
## Pattern syntax
#### (?name pattern)
Gives pattern a name, so matching node is also captured.
```js
jsstana.match("(binary ?op ?lhs (?rhs (or (literal) (ident))))");
```
#### (not pattern)
Matches when `pattern` doesn't match.
#### (or pattern1 pattern2...)
Matches if any pattern matches, returns first match.
#### (and pattern1 pattern2...)
Matches if all pattern matches, returns combined match.
### (nor pattern) and (nand pattern)
Are the same as `(not (or pattern))` and `(not (and pattern))` respectively.
#### (call callee arg0...argn)
Matches `CallExpression`.
`(call fun arg1 arg2)` matches exact amount of arguments,
for arbitrary arguments use
`(call fun ??params)`
#### (new class arg0...argn)
Matches `NewExpression`.
#### (ident name)
Matches `Identifier`.
#### (var name init)
Matches `VariableDeclarator`.
#### (null-node)
Matches `undefined` node.
#### (literal value)
Matches `Literal`.
There are some additional version::
- `(string value)` - string values
- `(number value)` - number values
- `(bool value)` - boolean values
- `(regexp value)` - regular expressions
- `(true)` - matches `true`
- `(false)` - matches `false`
- `(null)` - matches `null`
- `(infinity)` - matches `Infinity`
- `(nan)` - matches `NaN`, also `(NaN)` is supported
- `(undefined)` - matches `undefined`, also `(Infinity)` is supported
#### (this)
Matches `ThisExpression`.
#### (return value)
Matches `ReturnStatement`.
#### (expression expr)
Matches expression statement, `ExpressionStatement`.
#### (throw ex)
Matches `ThrowStatement`.
#### (break)
Matches `BreakStatement`.
#### (continue)
Matches `ContinueStatement`.
#### (member object property)
Matches `MemberExpression`.
- (property object property) matches non computed expressions, i.e. `foo.bar`.
- (subscript object property) matches computed expressions i.e. `foo[bar]`.
#### (lookup var.sub.name)
Helper macro for nested variable access.
`(lookup foo.bar.baz)` is equivalent to `(property (property foo bar) baz)`.
The atom `foo.bar.baz` works as `(lookup foo.bar.baz)`.
#### (binary op lhs rhs)
Matches `BinaryExpression`.
Also shorthand syntax is supported, `(+ a b)` is the same as `(binary + a b)`.
#### (logical op lhs rhs)
Matches `LogicalExpression`. ie. `&&` and `||` operators.
#### (unary op value)
Matches `UnaryExpression`.
Also shorthand version works for `!` and `~`: `(~ ?foo)` is the same as `(unary ~ ?foo)`.
#### (update op value)
Matches `UpdateExpression`.
You might want to use `postfix` and `prefix` though.
#### (assign op var value)
Matches `AssignmentExpression`.
#### (ternary test con alt)
Matches `ConditionalExpression`.
#### (fn-expr)
Matches `FunctionExpression`.
#### (object)
Matches `ObjectExpression`.
## API
### match(pattern, node)
Match `node` against `pattern`.
If pattern matches returns an object with match captures.
Otherwise returns `undefined`.
This function is autocurried ie. when one argument is passed, returns function `node -> matchresult`.
This function is also memoized on the pattern, ie each pattern is compiled only once.
### createMatcher(pattern, [posMatcher])
Create matcher. With one argument, `matcher(pattern) === match(pattern)`.
With additional arguments, you can add `$0`, `$1`... additional anonymous matchers.
```js
var matcher = jsstana.createMatcher("(expr (= a $0))", function (node) {
return node.type === "ObjectExpression" && node.properties.length === 0 ? {} : undefined;
});
```
### eslintRule(pattern, f)
### new jsstana()
Create new jsstana context. You can add new operations to this one.
```js
var ctx = new jsstana();
ctx.addMatchers("empty-object", function () {
this.assertArguments("empty-object", 0, arguments);
return function (node) {
return node.type === "ObjectExpression" && node.properties.length === 0 ? {} : undefined;
};
});
ctx.match("(empty-object", node);
```
You may compile submatchers with `this.matcher(sexpr)` and combine their results with `this.combineMatches`.
`this.assertArguments` checks argument (rator) count, to help validate pattern grammar.
## Contributing
In lieu of a formal styleguide, take care to maintain the existing coding style.
- Add unit tests for any new or changed functionality.
- Lint and test your code using [Grunt](http://gruntjs.com/).
- Use `istanbul cover grunt simplemocha` to run tests with coverage with [istanbul](http://gotwarlost.github.io/istanbul/).
- Create a pull request
## Release History
- 0.1.6 — *2015-08-28* — Depdenency update
- 0.1.5 — *2014-02-25* — Dependency bump
- 0.1.4 — *2014-11-09* – jsstana.eslintRule
- `(object)` matcher
- 0.1.3 Multiple multi-param matching groups in `(call)`
Example: `(call ? ?? 0 ??)` checks whether function has zero as any argument.
- 0.1.2 Fix bug, identifier could start with underscore: `_`
- 0.1.1 New (call) syntax
- `(call ?fun ?param ?params ?last-one)`
- 0.0.22 dependency updates
- 0.0.21 Use commander
- 0.0.20 dependency update
- 0.0.19 dependency updates
- 0.0.18 null checks
- Also updated dependencies
- 0.0.17 this, break & continue
- Added forementioned matchers
- 0.0.16 Updates
- Dependencies updated
- `fn-expr` matches function expressions
- 0.0.15 Updates
- Dependencies updated
- Introduce eslint
- Fix logical expressions: `&&` and `||`
- 0.0.14 Better cli experience
- Strip shebang by default
- Truncate long output lines
- Fancier colorize of jsgrep output
- Catch parse errors and unexisting files
- 0.0.13 nand, nor and ?
- node capturing
- nand and nor
- instanceof, typeof, delete and void operators
- 0.0.12 Code reogranization
- 0.0.11 User-provided patterns
- fixed installing on Windows
- assignment pattern
- anonymous matchers
- 0.0.10 ident pattern
- 0.0.9 Boolean patterns
- 0.0.8 Even more rands
- unary and update expressions
- drop `literal-` prefix (eg plain `string` now)
- shorthand binary op syntax `(+ a b)`
- shorthand lookup syntax
- 0.0.7 jsgrep, third try
- 0.0.6 jsgrep, second try
- 0.0.5 jsgrep
- also new expression
- 0.0.4 Binary and throw
- 0.0.3 More rands
- call dotted syntax
- literals
- expr - expression statement
- use grunt-literate to generate README.md
- 0.0.2 Dev setup
- 0.0.1 Preview release
Copyright Oleg Grenrus 2013
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