Lift Framework example source code file (json.js)

This example Lift Framework source code file (json.js) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lift Framework tags/keywords

boolean, date, date, number, regexp, regexp, string, string, syntaxerror, t, z, z

The Lift Framework json.js source code

/*
Copyright (c) 2008, Yahoo! Inc. All rights reserved.
Code licensed under the BSD License:
http://developer.yahoo.net/yui/license.txt
version: 2.6.0
*/
/**
 * Provides methods to parse JSON strings and convert objects to JSON strings.
 * @module json
 * @class JSON
 * @static
 */
YAHOO.lang.JSON = (function () {

var l = YAHOO.lang,

    /**
     * Replace certain Unicode characters that JavaScript may handle incorrectly
     * during eval--either by deleting them or treating them as line
     * endings--with escape sequences.
     * IMPORTANT NOTE: This regex will be used to modify the input if a match is
     * found.
     * @property _UNICODE_EXCEPTIONS
     * @type {RegExp}
     * @private
     */
    _UNICODE_EXCEPTIONS = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,

    /**
     * First step in the validation.  Regex used to replace all escape
     * sequences (i.e. "\\", etc) with '@' characters (a non-JSON character).
     * @property _ESCAPES
     * @type {RegExp}
     * @static
     * @private
     */
    _ESCAPES = /\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g,

    /**
     * Second step in the validation.  Regex used to replace all simple
     * values with ']' characters.
     * @property _VALUES
     * @type {RegExp}
     * @static
     * @private
     */
    _VALUES  = /"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g,

    /**
     * Third step in the validation.  Regex used to remove all open square
     * brackets following a colon, comma, or at the beginning of the string.
     * @property _BRACKETS
     * @type {RegExp}
     * @static
     * @private
     */
    _BRACKETS = /(?:^|:|,)(?:\s*\[)+/g,

    /**
     * Final step in the validation.  Regex used to test the string left after
     * all previous replacements for invalid characters.
     * @property _INVALID
     * @type {RegExp}
     * @static
     * @private
     */
    _INVALID  = /^[\],:{}\s]*$/,

    /**
     * Regex used to replace special characters in strings for JSON
     * stringification.
     * @property _SPECIAL_CHARS
     * @type {RegExp}
     * @static
     * @private
     */
    _SPECIAL_CHARS = /[\\\"\x00-\x1f\x7f-\x9f\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,

    /**
     * Character substitution map for common escapes and special characters.
     * @property _CHARS
     * @type {Object}
     * @static
     * @private
     */
    _CHARS = {
        '\b': '\\b',
        '\t': '\\t',
        '\n': '\\n',
        '\f': '\\f',
        '\r': '\\r',
        '"' : '\\"',
        '\\': '\\\\'
    };

/**
 * Traverses nested objects, applying a filter or reviver function to
 * each value.  The value returned from the function will replace the
 * original value in the key:value pair.  If the value returned is
 * undefined, the key will be omitted from the returned object.
 * @method _revive
 * @param data {MIXED} Any JavaScript data
 * @param reviver {Function} filter or mutation function
 * @return {MIXED} The results of the filtered/mutated data structure
 * @private
 */
function _revive(data, reviver) {
    var walk = function (o,key) {
        var k,v,value = o[key];
        if (value && typeof value === 'object') {
            for (k in value) {
                if (l.hasOwnProperty(value,k)) {
                    v = walk(value, k);
                    if (v === undefined) {
                        delete value[k];
                    } else {
                        value[k] = v;
                    }
                }
            }
        }
        return reviver.call(o,key,value);
    };

    return typeof reviver === 'function' ? walk({'':data},'') : data;
}

/**
 * Escapes a special character to a safe Unicode representation
 * @method _char
 * @param c {String} single character to escape
 * @return {String} safe Unicode escape
 */
function _char(c) {
    if (!_CHARS[c]) {
        _CHARS[c] =  '\\u'+('0000'+(+(c.charCodeAt(0))).toString(16)).slice(-4);
    }
    return _CHARS[c];
}

/**
 * Replace certain Unicode characters that may be handled incorrectly by
 * some browser implementations.
 * @method _prepare
 * @param s {String} parse input
 * @return {String} sanitized JSON string ready to be validated/parsed
 * @private
 */
function _prepare(s) {
    return s.replace(_UNICODE_EXCEPTIONS, _char);
}

/**
 * Four step determination whether a string is valid JSON.  In three steps,
 * escape sequences, safe values, and properly placed open square brackets
 * are replaced with placeholders or removed.  Then in the final step, the
 * result of all these replacements is checked for invalid characters.
 * @method _isValid
 * @param str {String} JSON string to be tested
 * @return {boolean} is the string safe for eval?
 * @static
 */
function _isValid(str) {
    return l.isString(str) &&
            _INVALID.test(str.
            replace(_ESCAPES,'@').
            replace(_VALUES,']').
            replace(_BRACKETS,''));
}

/**
 * Enclose escaped strings in quotes
 * @method _string
 * @param s {String} string to wrap
 * @return {String} '"'+s+'"' after s has had special characters escaped
 * @private
 */
function _string(s) {
    return '"' + s.replace(_SPECIAL_CHARS, _char) + '"';
}

/**
 * Worker function used by public stringify.
 * @method _stringify
 * @param h {Object} object holding the key
 * @param key {String} String key in object h to serialize
 * @param depth {Number} depth to serialize
 * @param w {Array|Function} array of whitelisted keys OR replacer function
 * @param pstack {Array} used to protect against recursion
 * @return {String} serialized version of o
 */
function _stringify(h,key,d,w,pstack) {
    var o = typeof w === 'function' ? w.call(h,key,h[key]) : h[key],
        i,len,j, // array iteration
        k,v,     // object iteration
        isArray, // forking in typeof 'object'
        a;       // composition array for performance over string concat

    if (o instanceof Date) {
        o = l.JSON.dateToString(o);
    } else if (o instanceof String || o instanceof Boolean || o instanceof Number) {
        o = o.valueOf();
    }

    switch (typeof o) {
        case 'string' : return _string(o);
        case 'number' : return isFinite(o) ? String(o) : 'null';
        case 'boolean': return String(o);
        case 'object' :
            // null
            if (o === null) {
                return 'null';
            }

            // Check for cyclical references
            for (i = pstack.length - 1; i >= 0; --i) {
                if (pstack[i] === o) {
                    return 'null';
                }
            }

            // Add the object to the processing stack
            pstack[pstack.length] = o;

            a = [];
            isArray = l.isArray(o);

            // Only recurse if we're above depth config
            if (d > 0) {
                // Array
                if (isArray) {
                    for (i = o.length - 1; i >= 0; --i) {
                        a[i] = _stringify(o,i,d-1,w,pstack) || 'null';
                    }

                // Object
                } else {
                    j = 0;
                    // Use whitelist keys if provided as an array
                    if (l.isArray(w)) {
                        for (i = 0, len = w.length; i < len; ++i) {
                            k = w[i];
                            v = _stringify(o,k,d-1,w,pstack);
                            if (v) {
                                a[j++] = _string(k) + ':' + v;
                            }
                        }
                    } else {
                        for (k in o) {
                            if (typeof k === 'string' && l.hasOwnProperty(o,k)) {
                                v = _stringify(o,k,d-1,w,pstack);
                                if (v) {
                                    a[j++] = _string(k) + ':' + v;
                                }
                            }
                        }
                    }

                    // sort object keys for easier readability
                    a.sort();
                }
            }

            // remove the object from the stack
            pstack.pop();

            return isArray ? '['+a.join(',')+']' : '{'+a.join(',')+'}';
    }

    return undefined; // invalid input
}

// Return the public API
return {
    /**
     * Four step determination whether a string is valid JSON.  In three steps,
     * escape sequences, safe values, and properly placed open square brackets
     * are replaced with placeholders or removed.  Then in the final step, the
     * result of all these replacements is checked for invalid characters.
     * @method isValid
     * @param str {String} JSON string to be tested
     * @return {boolean} is the string safe for eval?
     * @static
     */
    isValid : function (s) {
        return _isValid(_prepare(s));
    },

    /**
     * Parse a JSON string, returning the native JavaScript representation.
     * Only minor modifications from http://www.json.org/json2.js.
     * @param s {string} JSON string data
     * @param reviver {function} (optional) function(k,v) passed each key:value
     *          pair of object literals, allowing pruning or altering values
     * @return {MIXED} the native JavaScript representation of the JSON string
     * @throws SyntaxError
     * @method parse
     * @static
     */
    parse : function (s,reviver) {
        // sanitize
        s = _prepare(s);

        // Ensure valid JSON
        if (_isValid(s)) {
            // Eval the text into a JavaScript data structure, apply the
            // reviver function if provided, and return
            return _revive( eval('(' + s + ')'), reviver );
        }

        // The text is not valid JSON
        throw new SyntaxError('parseJSON');
    },

    /**
     * Converts an arbitrary value to a JSON string representation.
     * Cyclical object or array references are replaced with null.
     * If a whitelist is provided, only matching object keys will be included.
     * If a depth limit is provided, objects and arrays at that depth will
     * be stringified as empty.
     * @method stringify
     * @param o {MIXED} any arbitrary object to convert to JSON string
     * @param w {Array|Function} (optional) whitelist of acceptable object keys to include OR a function(value,key) to alter values before serialization
     * @param d {number} (optional) depth limit to recurse objects/arrays (practical minimum 1)
     * @return {string} JSON string representation of the input
     * @static
     */
    stringify : function (o,w,d) {
        if (o !== undefined) {
            // Ensure whitelist keys are unique (bug 2110391)
            if (l.isArray(w)) {
                w = (function (a) {
                    var uniq=[],map={},v,i,j,len;
                    for (i=0,j=0,len=a.length; i<len; ++i) {
                        v = a[i];
                        if (typeof v === 'string' && map[v] === undefined) {
                            uniq[(map[v] = j++)] = v;
                        }
                    }
                    return uniq;
                })(w);
            }

            // Default depth to POSITIVE_INFINITY
            d = d >= 0 ? d : 1/0;

            // process the input
            return _stringify({'':o},'',d,w,[]);
        }

        return undefined;
    },

    /**
     * Serializes a Date instance as a UTC date string.  Used internally by
     * stringify.  Override this method if you need Dates serialized in a
     * different format.
     * @method dateToString
     * @param d {Date} The Date to serialize
     * @return {String} stringified Date in UTC format YYYY-MM-DDTHH:mm:SSZ
     * @static
     */
    dateToString : function (d) {
        function _zeroPad(v) {
            return v < 10 ? '0' + v : v;
        }

        return d.getUTCFullYear()         + '-' +
            _zeroPad(d.getUTCMonth() + 1) + '-' +
            _zeroPad(d.getUTCDate())      + 'T' +
            _zeroPad(d.getUTCHours())     + ':' +
            _zeroPad(d.getUTCMinutes())   + ':' +
            _zeroPad(d.getUTCSeconds())   + 'Z';
    },

    /**
     * Reconstitute Date instances from the default JSON UTC serialization.
     * Reference this from a reviver function to rebuild Dates during the
     * parse operation.
     * @method stringToDate
     * @param str {String} String serialization of a Date
     * @return {Date}
     */
    stringToDate : function (str) {
        if (/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})Z$/.test(str)) {
            var d = new Date();
            d.setUTCFullYear(RegExp.$1, (RegExp.$2|0)-1, RegExp.$3);
            d.setUTCHours(RegExp.$4, RegExp.$5, RegExp.$6);
            return d;
        }
        return str;
    }
};

})();
YAHOO.register("json", YAHOO.lang.JSON, {version: "2.6.0", build: "1321"});