API: json JSON.js (YUI Library)

# Yahoo! UI Library

### json 2.8.1

Yahoo! UI Library > json > JSON.js (source view)
Search:
Filters Show Private Show Protected Show Deprecated

    /**
     * Provides methods to parse JSON strings and convert objects to JSON strings.
     *
     * @module json
     * @class JSON
     * @namespace YAHOO.lang
     * @static
     */
    (function () {

    var l = YAHOO.lang,
        isFunction = l.isFunction,
        isObject   = l.isObject,
        isArray    = l.isArray,
        _toStr     = Object.prototype.toString,
                     // 'this' is the global object.  window in browser env.  Keep
                     // the code env agnostic.  Caja requies window, unfortunately.
        Native     = (YAHOO.env.ua.caja ? window : this).JSON,

    /* Variables used by parse */

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

    /* Variables used by stringify */

        /**
         * 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',
            '"' : '\\"',
            '\\': '\\\\'
        },

        UNDEFINED = 'undefined',
        OBJECT    = 'object',
        NULL      = 'null',
        STRING    = 'string',
        NUMBER    = 'number',
        BOOLEAN   = 'boolean',
        DATE      = 'date',
        _allowable = {
            'undefined'        : UNDEFINED,
            'string'           : STRING,
            '[object String]'  : STRING,
            'number'           : NUMBER,
            '[object Number]'  : NUMBER,
            'boolean'          : BOOLEAN,
            '[object Boolean]' : BOOLEAN,
            '[object Date]'    : DATE,
            '[object RegExp]'  : OBJECT
        },
        EMPTY     = '',
        OPEN_O    = '{',
        CLOSE_O   = '}',
        OPEN_A    = '[',
        CLOSE_A   = ']',
        COMMA     = ',',
        COMMA_CR  = ",\n",
        CR        = "\n",
        COLON     = ':',
        COLON_SP  = ': ',
        QUOTE     = '"';

    // Only accept JSON objects that report a [[Class]] of JSON
    Native = _toStr.call(Native) === '[object JSON]' && Native;

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

    /* functions used by parse */

    /**
     * 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;
    }

    /**
     * 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);
    }

    function _isSafe(str) {
        return l.isString(str) &&
                _UNSAFE.test(str.replace(_ESCAPES,'@').
                                 replace(_VALUES,']').
                                 replace(_BRACKETS,''));
    }

    function _parse(s,reviver) {
        // sanitize
        s = _prepare(s);

        // Ensure valid JSON
        if (_isSafe(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('JSON.parse');
    }

    /* functions used by stringify */

    // Utility function used to determine how to serialize a variable.
    function _type(o) {
        var t = typeof o;
        return  _allowable[t] ||              // number, string, boolean, undefined
                _allowable[_toStr.call(o)] || // Number, String, Boolean, Date
                (t === OBJECT ?
                    (o ? OBJECT : NULL) :     // object, array, null, misc natives
                    UNDEFINED);               // function, unknown
    }

    // Enclose escaped strings in quotes
    function _string(s) {
        return QUOTE + s.replace(_SPECIAL_CHARS, _char) + QUOTE;
    }

    // Adds the provided space to the beginning of every line in the input string
    function _indent(s,space) {
        return s.replace(/^/gm, space);
    }

    // JavaScript implementation of stringify (see API declaration of stringify)
    function _stringify(o,w,space) {
        if (o === undefined) {
            return undefined;
        }

        var replacer = isFunction(w) ? w : null,
            format   = _toStr.call(space).match(/String|Number/) || [],
            _date    = YAHOO.lang.JSON.dateToString,
            stack    = [],
            tmp,i,len;

        if (replacer || !isArray(w)) {
            w = undefined;
        }

        // Ensure whitelist keys are unique (bug 2110391)
        if (w) {
            tmp = {};
            for (i = 0, len = w.length; i < len; ++i) {
                tmp[w[i]] = true;
            }
            w = tmp;
        }

        // Per the spec, strings are truncated to 10 characters and numbers
        // are converted to that number of spaces (max 10)
        space = format[0] === 'Number' ?
                    new Array(Math.min(Math.max(0,space),10)+1).join(" ") :
                    (space || EMPTY).slice(0,10);

        function _serialize(h,key) {
            var value = h[key],
                t     = _type(value),
                a     = [],
                colon = space ? COLON_SP : COLON,
                arr, i, keys, k, v;

            // Per the ECMA 5 spec, toJSON is applied before the replacer is
            // called.  Also per the spec, Date.prototype.toJSON has been added, so
            // Date instances should be serialized prior to exposure to the
            // replacer.  I disagree with this decision, but the spec is the spec.
            if (isObject(value) && isFunction(value.toJSON)) {
                value = value.toJSON(key);
            } else if (t === DATE) {
                value = _date(value);
            }

            if (isFunction(replacer)) {
                value = replacer.call(h,key,value);
            }

            if (value !== h[key]) {
                t = _type(value);
            }

            switch (t) {
                case DATE    : // intentional fallthrough.  Pre-replacer Dates are
                               // serialized in the toJSON stage.  Dates here would
                               // have been produced by the replacer.
                case OBJECT  : break;
                case STRING  : return _string(value);
                case NUMBER  : return isFinite(value) ? value+EMPTY : NULL;
                case BOOLEAN : return value+EMPTY;
                case NULL    : return NULL;
                default      : return undefined;
            }

            // Check for cyclical references in nested objects
            for (i = stack.length - 1; i >= 0; --i) {
                if (stack[i] === value) {
                    throw new Error("JSON.stringify. Cyclical reference");
                }
            }

            arr = isArray(value);

            // Add the object to the processing stack
            stack.push(value);

            if (arr) { // Array
                for (i = value.length - 1; i >= 0; --i) {
                    a[i] = _serialize(value, i) || NULL;
                }
            } else {   // Object
                // If whitelist provided, take only those keys
                keys = w || value;
                i = 0;

                for (k in keys) {
                    if (keys.hasOwnProperty(k)) {
                        v = _serialize(value, k);
                        if (v) {
                            a[i++] = _string(k) + colon + v;
                        }
                    }
                }
            }

            // remove the array from the stack
            stack.pop();

            if (space && a.length) {
                return arr ?
                    OPEN_A + CR + _indent(a.join(COMMA_CR), space) + CR + CLOSE_A :
                    OPEN_O + CR + _indent(a.join(COMMA_CR), space) + CR + CLOSE_O;
            } else {
                return arr ?
                    OPEN_A + a.join(COMMA) + CLOSE_A :
                    OPEN_O + a.join(COMMA) + CLOSE_O;
            }
        }

        // process the input
        return _serialize({'':o},'');
    }

    /* Public API */
    YAHOO.lang.JSON = {
        /**
         * Leverage native JSON parse if the browser has a native implementation.
         * In general, this is a good idea.  See the Known Issues section in the
         * JSON user guide for caveats.  The default value is true for browsers with
         * native JSON support.
         *
         * @property useNativeParse
         * @type Boolean
         * @default true
         * @static
         */
        useNativeParse : !!Native,

        /**
         * Leverage native JSON stringify if the browser has a native
         * implementation.  In general, this is a good idea.  See the Known Issues
         * section in the JSON user guide for caveats.  The default value is true
         * for browsers with native JSON support.
         *
         * @property useNativeStringify
         * @type Boolean
         * @default true
         * @static
         */
        useNativeStringify : !!Native,

        /**
         * Four step determination whether a string is safe to eval. 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 isSafe
         * @param str {String} JSON string to be tested
         * @return {boolean} is the string safe for eval?
         * @static
         */
        isSafe : function (s) {
            return _isSafe(_prepare(s));
        },

        /**
         * <p>Parse a JSON string, returning the native JavaScript
         * representation.</p>
         *
         * <p>When lang.JSON.useNativeParse is true, this will defer to the native
         * JSON.parse if the browser has a native implementation.  Otherwise, a
         * JavaScript implementation based on http://www.json.org/json2.js
         * is used.</p>
         *
         * @method parse
         * @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
         * @static
         */
        parse : function (s,reviver) {
            return Native && YAHOO.lang.JSON.useNativeParse ?
                Native.parse(s,reviver) : _parse(s,reviver);
        },

        /**
         * <p>Converts an arbitrary value to a JSON string representation.</p>
         *
         * <p>Objects with cyclical references will trigger an exception.</p>
         *
         * <p>If a whitelist is provided, only matching object keys will be
         * included.  Alternately, a replacer function may be passed as the
         * second parameter.  This function is executed on every value in the
         * input, and its return value will be used in place of the original value.
         * This is useful to serialize specialized objects or class instances.</p>
         *
         * <p>If a positive integer or non-empty string is passed as the third
         * parameter, the output will be formatted with carriage returns and
         * indentation for readability.  If a String is passed (such as "\t") it
         * will be used once for each indentation level.  If a number is passed,
         * that number of spaces will be used.</p>
         *
         * <p>When lang.JSON.useNativeStringify is true, this will defer to the
         * native JSON.stringify if the browser has a native implementation.
         * Otherwise, a JavaScript implementation is used.</p>
         *
         * @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 space {Number|String} (optional) indentation character(s) or
         *                  depthy of spaces to format the output
         * @return {string} JSON string representation of the input
         * @throws Error
         * @static
         */
        stringify : function (o,w,space) {
            return Native && YAHOO.lang.JSON.useNativeStringify ?
                Native.stringify(o,w,space) : _stringify(o,w,space);
        },

        /**
         * Serializes a Date instance as a UTC date string.  Used internally by
         * the JavaScript implementation of stringify.  If you need a different
         * Date serialization format, override this method.  If you change this,
         * you should also set useNativeStringify to false, since native JSON
         * implementations serialize Dates per the ECMAScript 5 spec.  You've been
         * warned.
         *
         * @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())     + COLON +
                _zeroPad(d.getUTCMinutes())   + COLON +
                _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) {
            var m = str.match(/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})(?:\.(\d{3}))?Z$/);
            if (m) {
                var d = new Date();
                d.setUTCFullYear(m[1], m[2]-1, m[3]);
                d.setUTCHours(m[4], m[5], m[6], (m[7] || 0));
                return d;
            }
            return str;
        }
    };

    /**
     * <p>Four step determination whether a string is safe to eval. 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.</p>
     *
     * <p>This is an alias for isSafe.</p>
     *
     * @method isValid
     * @param str {String} JSON string to be tested
     * @return {boolean} is the string safe for eval?
     * @static
     * @deprecated use isSafe
     */
    YAHOO.lang.JSON.isValid = YAHOO.lang.JSON.isSafe;

    })();

Copyright © 2010 Yahoo! Inc. All rights reserved.