querystring.js

// Query String Utilities

var DEFAULT_SEP = "&";
var DEFAULT_EQ = "=";

exports.unescape = function (str, decodeSpaces) {
    return decodeURIComponent(decodeSpaces ? str.replace(/\+/g, " ") : str);
};

exports.escape = function (str) {
    return encodeURIComponent(str);
};

exports.toQueryString = function (obj, sep, eq, name) {
    sep = sep || DEFAULT_SEP;
    eq = eq || DEFAULT_EQ;
    if (isA(obj, null) || isA(obj, undefined)) {
        return name ? encodeURIComponent(name) + eq : '';
    }
    if (isNumber(obj) || isString(obj)) {
        return encodeURIComponent(name) + eq + encodeURIComponent(obj);
    }
    if (isA(obj, [])) {
        var s = [];
        name = name+'[]';
        for (var i = 0, l = obj.length; i < l; i ++) {
            s.push( exports.toQueryString(obj[i], sep, eq, name) );
        }
        return s.join(sep);
    }
    // now we know it's an object.
    var s = [];
    var begin = name ? name + '[' : '';
    var end = name ? ']' : '';
    for (var i in obj) if (obj.hasOwnProperty(i)) {
        var n = begin + i + end;
        s.push(exports.toQueryString(obj[i], sep, eq, n));
    }
    return s.join(sep);
};

exports.parseQuery = function(qs, sep, eq) {
    return qs
        .split(sep||DEFAULT_SEP)
        .map(pieceParser(eq||DEFAULT_EQ))
        .reduce(mergeParams);
};
        
// 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"}]}}
var pieceParser = function (eq) {
    return function parsePiece (key, val) {
        if (arguments.length !== 2) {
            // key=val, called from the map/reduce
             key = key.split(eq);
            return parsePiece(
                exports.unescape(key.shift(), true), exports.unescape(key.join(eq), true)
            );
        }
        key = key.replace(/^\s+|\s+$/g, '');
        if (isString(val)) val = val.replace(/^\s+|\s+$/g, '');
        var sliced = /(.*)\[([^\]]*)\]$/.exec(key);
        if (!sliced) {
            var ret = {};
            if (key) ret[key] = val;
            return ret;
        }
        // ["foo[][bar][][baz]", "foo[][bar][]", "baz"]
        var tail = sliced[2], head = sliced[1];
    
        // array: key[]=val
        if (!tail) return parsePiece(head, [val]);
    
        // obj: key[subkey]=val
        var ret = {};
        ret[tail] = val;
        return parsePiece(head, ret);
    };
};

// the reducer function that merges each query piece together into one set of params
function mergeParams (params, addition) {
    return (
        // if it's uncontested, then just return the addition.
        (!params) ? addition
        // if the existing value is an array, then concat it.
        : (isA(params, [])) ? params.concat(addition)
        // if the existing value is not an array, and either are not objects, arrayify it.
        : (!isA(params, {}) || !isA(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.
function mergeObjects (params, addition) {
    for (var i in addition) if (i && addition.hasOwnProperty(i)) {
        params[i] = mergeParams(params[i], addition[i]);
    }
    return params;
};

// duck typing
function isA (thing, canon) {
    return (
        // truthiness. you can feel it in your gut.
        (!thing === !canon)
        // typeof is usually "object"
        && typeof(thing) === typeof(canon)
        // check the constructor
        && Object.prototype.toString.call(thing) === Object.prototype.toString.call(canon)
    );
};
function isNumber (thing) {
    return typeof(thing) === "number" && isFinite(thing);
};
function isString (thing) {
    return typeof(thing) === "string";
};