# Yahoo! UI Library

### querystring 3.3.0

Yahoo! UI Library > querystring > querystring-parse.js (source view)
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    /**
     * <p>The QueryString module adds support for serializing JavaScript objects into
     * query strings and parsing JavaScript objects from query strings format.</p>
     *
     * <p>The QueryString namespace is added to your YUI instance including static methods
     * Y.QueryString.parse(..) and Y.QueryString.stringify(..).</p>
     *
     * <p>The <code>querystring</code> module is a rollup of <code>querystring-parse</code> and
     * <code>querystring-stringify</code>.</p>
     *
     * <p>As their names suggest, <code>querystring-parse</code> adds support for parsing
     * Query String data (Y.QueryString.parse) and <code>querystring-stringify</code> for serializing
     * JavaScript data into Query Strings (Y.QueryString.stringify).  You may choose to
     * include either of the submodules individually if you don't need the
     * complementary functionality, or include the rollup for both.</p>
     *
     * @module querystring
     * @class QueryString
     * @static
     */
    var QueryString = Y.namespace("QueryString"),

    // Parse a key=val string.
    // These can get pretty hairy
    // example flow:
    // parse(foo[bar][][bla]=baz)
    // return parse(foo[bar][][bla],"baz")
    // return parse(foo[bar][], {bla : "baz"})
    // return parse(foo[bar], [{bla:"baz"}])
    // return parse(foo, {bar:[{bla:"baz"}]})
    // return {foo:{bar:[{bla:"baz"}]}}
    pieceParser = function (eq) {
        return function parsePiece (key, val) {

            var sliced, numVal, head, tail, ret;

            if (arguments.length !== 2) {
                // key=val, called from the map/reduce
                key = key.split(eq);
                return parsePiece(
                    QueryString.unescape(key.shift()),
                    QueryString.unescape(key.join(eq))
                );
            }
            key = key.replace(/^\s+|\s+$/g, '');
            if (Y.Lang.isString(val)) {
                val = val.replace(/^\s+|\s+$/g, '');
                // convert numerals to numbers
                if (!isNaN(val)) {
                    numVal = +val;
                    if (val === numVal.toString(10)) {
                        val = numVal;
                    }
                }
            }
            sliced = /(.*)\[([^\]]*)\]$/.exec(key);
            if (!sliced) {
                ret = {};
                if (key) {
                    ret[key] = val;
                }
                return ret;
            }
            // ["foo[][bar][][baz]", "foo[][bar][]", "baz"]
            tail = sliced[2];
            head = sliced[1];

            // array: key[]=val
            if (!tail) {
                return parsePiece(head, [val]);
            }

            // obj: key[subkey]=val
            ret = {};
            ret[tail] = val;
            return parsePiece(head, ret);
        };
    },

    // the reducer function that merges each query piece together into one set of params
    mergeParams = function(params, addition) {
        return (
            // if it's uncontested, then just return the addition.
            (!params) ? addition
            // if the existing value is an array, then concat it.
            : (Y.Lang.isArray(params)) ? params.concat(addition)
            // if the existing value is not an array, and either are not objects, arrayify it.
            : (!Y.Lang.isObject(params) || !Y.Lang.isObject(addition)) ? [params].concat(addition)
            // else merge them as objects, which is a little more complex
            : mergeObjects(params, addition)
        );
    },

    // Merge two *objects* together. If this is called, we've already ruled
    // out the simple cases, and need to do the for-in business.
    mergeObjects = function(params, addition) {
        for (var i in addition) {
            if (i && addition.hasOwnProperty(i)) {
                params[i] = mergeParams(params[i], addition[i]);
            }
        }
        return params;
    };

    /**
     * Provides Y.QueryString.parse method to accept Query Strings and return native
     * JavaScript objects.
     *
     * @module querystring
     * @submodule querystring-parse
     * @for QueryString
     * @method parse
     * @param qs {String} Querystring to be parsed into an object.
     * @param sep {String} (optional) Character that should join param k=v pairs together. Default: "&"
     * @param eq  {String} (optional) Character that should join keys to their values. Default: "="
     * @public
     * @static
     */
    QueryString.parse = function (qs, sep, eq) {
        // wouldn't Y.Array(qs.split()).map(pieceParser(eq)).reduce(mergeParams) be prettier?
        return Y.Array.reduce(
            Y.Array.map(
                qs.split(sep || "&"),
                pieceParser(eq || "=")
            ),
            {},
            mergeParams
        );
    };

    /**
     * Provides Y.QueryString.unescape method to be able to override default decoding
     * method.  This is important in cases where non-standard delimiters are used, if
     * the delimiters would not normally be handled properly by the builtin
     * (en|de)codeURIComponent functions.
     * Default: replace "+" with " ", and then decodeURIComponent behavior.
     * @module querystring
     * @submodule querystring-parse
     * @for QueryString
     * @method unescape
     * @param s {String} String to be decoded.
     * @public
     * @static
     **/
    QueryString.unescape = function (s) {
        return decodeURIComponent(s.replace(/\+/g, ' '));
    };

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