json2.js

来自「一个实用的CMS管理」· JavaScript 代码 · 共 480 行 · 第 1/2 页

// If we were called with a replacer function, then call the replacer to
// obtain a replacement value.

            if (typeof rep === 'function') {
                value = rep.call(holder, key, value);
            }

// What happens next depends on the value's type.

            switch (typeof value) {
            case 'string':
                return quote(value);

            case 'number':

// JSON numbers must be finite. Encode non-finite numbers as null.

                return isFinite(value) ? String(value) : 'null';

            case 'boolean':
            case 'null':

// If the value is a boolean or null, convert it to a string. Note:
// typeof null does not produce 'null'. The case is included here in
// the remote chance that this gets fixed someday.

                return String(value);

// If the type is 'object', we might be dealing with an object or an array or
// null.

            case 'object':

// Due to a specification blunder in ECMAScript, typeof null is 'object',
// so watch out for that case.

                if (!value) {
                    return 'null';
                }

// Make an array to hold the partial results of stringifying this object value.

                gap += indent;
                partial = [];

// If the object has a dontEnum length property, we'll treat it as an array.

                if (typeof value.length === 'number' &&
                        !(value.propertyIsEnumerable('length'))) {

// The object is an array. Stringify every element. Use null as a placeholder
// for non-JSON values.

                    length = value.length;
                    for (i = 0; i < length; i += 1) {
                        partial[i] = str(i, value) || 'null';
                    }

// Join all of the elements together, separated with commas, and wrap them in
// brackets.

                    v = partial.length === 0 ? '[]' :
                        gap ? '[' + breaker + gap +
                                partial.join(',' + breaker + gap) + breaker +
                                    mind + ']' :
                              '[' + partial.join(',') + ']';
                    gap = mind;
                    return v;
                }

// If the replacer is an array, use it to select the members to be stringified.

                if (rep && typeof rep === 'object') {
                    length = rep.length;
                    for (i = 0; i < length; i += 1) {
                        k = rep[i];
                        if (typeof k === 'string') {
                            v = str(k, value, rep);
                            if (v) {
                                partial.push(quote(k) + (gap ? ': ' : ':') + v);
                            }
                        }
                    }
                } else {

// Otherwise, iterate through all of the keys in the object.

                    for (k in value) {
                        if (Object.hasOwnProperty.call(value, k)) {
                            v = str(k, value, rep);
                            if (v) {
                                partial.push(quote(k) + (gap ? ': ' : ':') + v);
                            }
                        }
                    }
                }

// Join all of the member texts together, separated with commas,
// and wrap them in braces.

                v = partial.length === 0 ? '{}' :
                    gap ? '{' + breaker + gap +
                            partial.join(',' + breaker + gap) + breaker +
                            mind + '}' :
                          '{' + partial.join(',') + '}';
                gap = mind;
                return v;
            }
        }


// Return the JSON object containing the stringify, parse, and quote methods.

        return {
            stringify: function (value, replacer, space, linebreak) {

// The stringify method takes a value and an optional replacer, and an optional
// space parameter, and returns a JSON text. The replacer can be a function
// that can replace values, or an array of strings that will select the keys.
// A default replacer method can be provided. Use of the space parameter can
// produce text that is more easily readable.

                var i;
                gap = '';
                indent = '';
                if (space) {

// If the space parameter is a number, make an indent string containing that
// many spaces.

                    if (typeof space === 'number') {
                        for (i = 0; i < space; i += 1) {
                            indent += ' ';
                        }

// If the space parameter is a string, it will be used as the indent string.

                    } else if (typeof space === 'string') {
                        indent = space;
                    }
                    breaker = typeof linebreak !== 'string' ? '\n' : linebreak;
                }

// If there is a replacer, it must be a function or an array.
// Otherwise, throw an error.

                rep = replacer;
                if (replacer && typeof replacer !== 'function' &&
                        (typeof replacer !== 'object' ||
                         typeof replacer.length !== 'number')) {
                    throw new Error('JSON.stringify');
                }

// Make a fake root object containing our value under the key of ''.
// Return the result of stringifying the value.

                return str('', {'': value});
            },


            parse: function (text, reviver) {

// The parse method takes a text and an optional reviver function, and returns
// a JavaScript value if the text is a valid JSON text.

                var j;

                function walk(holder, key) {

// The walk method is used to recursively walk the resulting structure so
// that modifications can be made.

                    var k, v, value = holder[key];
                    if (value && typeof value === 'object') {
                        for (k in value) {
                            if (Object.hasOwnProperty.call(value, k)) {
                                v = walk(value, k);
                                if (v !== undefined) {
                                    value[k] = v;
                                } else {
                                    delete value[k];
                                }
                            }
                        }
                    }
                    return reviver.call(holder, key, value);
                }


// Parsing happens in four stages. In the first stage, we replace certain
// Unicode characters with escape sequences. JavaScript handles many characters
// incorrectly, either silently deleting them, or treating them as line endings.

                if (cx.test(text)) {
                    text = text.replace(cx, function (a) {
                        return '\\u' + ('0000' +
                                (+(a.charCodeAt(0))).toString(16)).slice(-4);
                    });
                }

// In the second stage, we run the text against
// regular expressions that look for non-JSON patterns. We are especially
// concerned with '()' and 'new' because they can cause invocation, and '='
// because it can cause mutation. But just to be safe, we want to reject all
// unexpected forms.

// We split the second stage into 4 regexp operations in order to work around
// crippling inefficiencies in IE's and Safari's regexp engines. First we
// replace all backslash pairs with '@' (a non-JSON character). Second, we
// replace all simple value tokens with ']' characters. Third, we delete all
// open brackets that follow a colon or comma or that begin the text. Finally,
// we look to see that the remaining characters are only whitespace or ']' or
// ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.

                if (/^[\],:{}\s]*$/.test(text.replace(/\\["\\\/bfnrtu]/g, '@').
replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']').
replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) {

// In the third stage we use the eval function to compile the text into a
// JavaScript structure. The '{' operator is subject to a syntactic ambiguity
// in JavaScript: it can begin a block or an object literal. We wrap the text
// in parens to eliminate the ambiguity.

                    j = eval('(' + text + ')');

// In the optional fourth stage, we recursively walk the new structure, passing
// each name/value pair to a reviver function for possible transformation.

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

// If the text is not JSON parseable, then a SyntaxError is thrown.

                throw new SyntaxError('JSON.parse');
            }
        };
    }();
}