json loose parser

json_loose.js

if(!JSON){
    JSON = {};
}
(function(global, undef){

    "use strict";

    var ch,
        pos = 0,
        text,
        error = function (m) {
            throw {
                name: "SyntaxError",
                message: m,
                at: pos,
                text: text
            };
        },
        escapeChars = {
            "\"":  "\"",
            "\\": "\\",
            "/":  "/",
            b:    "\b",
            f:    "\f",
            n:    "\n",
            r:    "\r",
            t:    "\t"
        },
        skip = function(){
            while (ch && ch <= " ") {
                next();
            }
        },
        next = function () {
            ch = text.charAt(pos);
            pos += 1;
            return ch;
        },
        string = function(){
            var quote,
                result = "",
                uffff, i, hex;

            if(ch === '"' || ch === "'"){
                quote = ch;
                while(next()){
                    if(ch === quote){
                        next();
                        return result;
                    }
                    if(ch === "\\"){
                        if (ch === 'u') {
                            uffff = 0;
                            for (i = 0; i < 4; i += 1) {
                                hex = parseInt(next(), 16);
                                if (!isFinite(hex)) {
                                    break;
                                }
                                uffff = uffff * 16 + hex;
                            }
                            result += String.fromCharCode(uffff);
                        } else if (typeof escapeChars[ch] === 'string') {
                            result += escapeChars[ch];
                        } else {
                            break;
                        }
                    } else {
                        result += ch;
                    }
                }

            }
            error("Bad string");
        },
        object = function(){
            var key,
                result = {};

            if (ch === "{") {
                next();
                skip();

                if (ch === "}") {
                    next();
                    return result;   // empty object
                }

                while (ch) {
                    key = value(true);
                    skip();
                    if(ch !== ":"){
                        error("Bad object");
                    }
                    next();
                    if (Object.hasOwnProperty.call(result, key)) {
                        error("Duplicate key \"" + key + "\"");
                    }
                    result[key] = value();
                    skip();
                    if (ch === "}") {
                        next();
                        return result;
                    }
                    if(ch !== ","){
                        error("Bad object");
                    }
                    next();
                    skip();
                }
            }
            error("Bad object");
        },
        array = function () {

            var result = [];

            if (ch === "[") {
                next();
                skip();
                if (ch === "]") {
                    next();
                    return result;   // empty array
                }
                while (ch) {
                    result.push(value());
                    skip();
                    if (ch === ']') {
                        next();
                        return result;
                    }
                    next();
                    skip();
                }
            }
            error("Bad array");
        },
        loose = function(){
            var result = "";

            if(ch === "{"){
                return object();
            }
            if(ch === "["){
                return array();
            }
            if(ch === "\"" || ch === "'"){
                return string();
            }

            while(ch){
                if(ch === "," || ch === ":" || ch === "]" || ch === "}"){
                    return convert(result);
                }
                result += ch;
                next();
            }

            return convert(result);
        },
        convert = function(val){
            var upperVal;
            if(!val){
                return val;
            }
            //trim
            val = val.toString().replace(/(^\s+)|(\s+$)/g, "");
            upperVal = val.toUpperCase();
            if(upperVal === "TRUE" || upperVal === "FALSE"){
                return upperVal === "TRUE";
            }
            if(upperVal === "NULL"){
                return null;
            }
            if(upperVal === "NaN"){
                return NaN;
            }
            if(upperVal === "UNDEFINED"){
                return undef;
            }
            if(upperVal === "INFINITY"){
                return Infinity;
            }
            // isNumeric
            if(!isNaN( parseFloat(val) ) && isFinite( val )){
                return parseFloat(val);
            }
            return val;
        },
        value = function(primitive){

            skip();
            switch (ch) {
                case "{":
                    if(primitive){
                        error("Bad value");
                    }
                    return object();
                case "[":
                    if(primitive){
                        error("Bad value");
                    }
                    return array();
                case "\"":
                case "'":
                    return string();
                default:
                    return loose();
            }
        };

    JSON.parseLoose = function(source, reviver){
        var result;

        ch = " ";
        pos = 0;
        text = source;
        result = value();

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