parsley is a simple language for data-extraction from XML-like documents (including HTML). parsley is:
- Blazing fast -- Typical HTML parses are sub-50ms.
- Easy to write and understand -- parsley uses your current knowledge of JSON, CSS, and XPath.
- Powerful. parsley can understand full XPath, including standard and user-defined functions.
A simple script, or "parslet", looks like this:
{
"title": "h1",
"links(a)": [
{
"text": ".",
"href": "@href"
}
]
}
This returns JSON or XML output with the same structure. Applying this parslet to http://www.yelp.com/biz/amnesia-san-francisco yields either:
{
"title": "Amnesia",
"links": [
{
"href": "\/",
"text": "Yelp"
},
{
"href": "\/",
"text": "Welcome"
},
{
"href": "\/signup?return_url=%2Fuser_details",
"text": " About Me"
},
.....
]
}
or equivalently:
<parsley:root>
<title>Amnesia</title>
<links>
<parsley:group>
<href>/</href>
<text>Yelp</text>
</parsley:group>
<parsley:group>
<href>/</href>
<text>Welcome</text>
</parsley:group>
<parsley:group>
<href>/signup?return_url=%2Fuser_details</href>
<text> About Me</text>
</parsley:group>
.....
</links>
</parsley:root>
This parslet could also have been expressed as:
{
"title": "h1",
"links(a)": [
{
"text": ".",
"href": "@href"
}
]
}
The "a" in links(a) is a "key selector" -- an explicit grouping (with scope) for the array. You can use any XPath 1.0 or CSS3 expression as a value or a key selector. Parsley will try to be smart, and figure out which you are using. You can use CSS selectors inside XPath functions -- "substring-after(h1>a, ':')" is a valid expression.
You can use $foo to access the value of the key "foo" in the current scope (i.e. nested curly brace depth). Also available are $parent.foo, $parent.parent.foo, $root.foo, $root.foo.bar, etc.�
You can write custom functions in XSLT (I'd like to also support C and JavaScript). They look like:
<func:function name="user:excited">
<xsl:param name="input" />
<func:result select="concat($input, '!!!!!!!')" />
</func:function>
If you run:
{
"title": "user:excited(h1)",
}
on the Yelp page, you'll get:
{
"title": "Amnesia!!!!!!!",
}