A simple helper to extract values from a string based on a pattern.

extract_values.js

var extractValues = function(str, pattern, options) {
	options = options || {};
	var delimiters = options.delimiters || ["{", "}"];
	var lowercase = options.lowercase;
	var whitespace = options.whitespace;

	var special_chars_regex = /[\\\^\$\*\+\.\?\(\)]/g;
	var token_regex = new RegExp( delimiters[0] + "([^" + delimiters.join("") + "\t\r\n]+)" + delimiters[1], "g");
	var tokens = pattern.match(token_regex);
	var pattern_regex = new RegExp(pattern.replace(special_chars_regex, "\\$&").replace(token_regex, "(\.+)"));

	if (lowercase) {
		str = str.toLowerCase();
	}

	if (whitespace) {
		str = str.replace(/\s+/g, function(match) {
			var whitespace_str = "";
			for (var i = 0; i < whitespace; i++) {
				whitespace_str = whitespace_str + match.charAt(0);
			};
			return whitespace_str;
		});
	};

	var matches = str.match(pattern_regex)

	if (!matches) {
		return null;
	}

	matches = matches.splice(1);
	var output = {};
	for (var i=0; i < tokens.length; i++) {
		output[tokens[i].replace( new RegExp( delimiters[0] + "|" + delimiters[1], "g"), "")] = matches[i];
	}

	return output;
}

/* 
Examples
extractValues("/2012/08/12/test.html", "/{year}/{month}/{day}/{title}.html")
>> { "year": "2012", "month": "08", "day": "12", "title": "test" }

extractValues("John Doe <[email protected]> (http://example.com)", "{name} <{email}> ({url})")
>> {"name": "John Doe", "email": "[email protected]", "url": "http://example.com" }

extractValues("from 4th October  to 10th  October", "from `from` to `to`", { whitespace: 1, delimiters: ["`", "`"] })
>> {"from": "4th October", "to": "10th October" }

    extractValues("Convert 1500 Grams to Kilograms", "convert {quantity} {from_unit} to {to_unit}", { lowercase: true })
>> {"quantity": "1500", "from_unit": "grams", "to_unit": "kilograms" }]

*/