Records log messages and sends report to server in case of any error or warning.

TopLogger.js

function TopLogger(url, sessionId) {
    var self = this;
    var sid = sessionId;
    var counter = 0;
    var entries = [];


    function consoleLog(type, msg) {
        if(consoleChain && consoleChain[type]) {
            try {
                consoleChain[type].call(consoleChain.oldConsole, msg);
            } catch(e) {}
        }
    }

    function fillTemplate(subject, obj) {
        return subject.replace(/{([^{}]*)}/g,
            function (a, b) {
                return params[b];
            }
        );
    }

    function internalLog(level, sid, ar) {
        reloadSid();
        var args = Array.prototype.slice.call(ar);
        var message = args.shift();
        // message in a form ["test {1} and {2}", "par1", 123]
        if(typeof message === 'array' && message.length > 0) {
            message = message[0].template(message);
        } else {
            message = JSON.stringify(message);
        }
        if(args.length > 0) {
            for(var i = 0; i < args.length; i++) {
                message += ", " + JSON.stringify(args[i]);
            }
        }

        var entry = {level:level, sid:sid, counter: ++counter, message:message};
        entries.push(entry);
        return ""+level+" "+sid+":"+entry.counter+" "+message;
    }

    function flush() {
        if(entries.length > 0) {
            var local_ent = entries;
            entries = [];
            try {
                var xhr = new XMLHttpRequest();
                xhr.open("POST", url, true);
                xhr.setRequestHeader('Content-Type', 'application/json');
                xhr.send(JSON.stringify(local_ent));
            } catch(xhrerr) {
                //nothing can do here
                consoleLog('error', "Logger XHR failed");
            }
        }
    }

    function error() {
        try {
            consoleLog('error', internalLog('E', sid, arguments));
            flush();
        } catch (e) {
            //shit
        }
    }

    function log() {
        try {
            consoleLog('log', internalLog('D', sid, arguments));
        } catch (e) {
            //shit
        }
    }

    function warn() {
        try {
            consoleLog('warn', internalLog('W', sid, arguments));
            flush();
        } catch (e) {
            //shit
        }
    }

    function info() {
        try {
            consoleLog('info', internalLog('I', sid, arguments));
        } catch (e) {
            //shit
        }
    }

    this.e = error;
    this.w = warn;
    this.i = info;
    this.d = log;
    this.reset = function() {
        counter = 0;
        entries = [];
    };

    function onErrorHandler(old, args) {
        error(['ERR00:{1} ({2}:{3}:{4})',args[0],args[1],args[2],args[3], args[4]]);
        if (old) {
            old.apply(window, args);
        }
    }

    function reloadSid() {
        if(sid == null) {
            try {
                sid = window.localStorage.getItem("user.email");
                if(sid != null) {
                    var el = entries.length;
                    for (var i = 0; i < el; i++) {
                        entries[i].sid = sid;
                    }
                }
            } catch (e) {
                //local storage failed
            }
        }
    }

    //override onerror

    var oldOnError = window.onerror;
    window.onerror = function() {
        var args = Array.prototype.slice.call(arguments, 0);
        onErrorHandler(oldOnError, args);
    };

    //override console
    var consoleChain = null;
    if(window.console) {
        consoleChain = {
            info: window.console.info,
            error: window.console.error,
            warn: window.console.warn,
            log: window.console.log,
            oldConsole: window.console
        };
        window.console.error = function(msg) { self.e(msg); };
        window.console.warn = function(msg) { self.w(msg); };
        window.console.info = function(msg) { self.i(msg); };
        window.console.log = function(msg) { self.d(msg); };
    } else {

    }

    log("KPLogger: " + window.location.pathname + ", " + navigator.userAgent);
}

if(typeof LOG === 'undefined') {
    var LOG = new TopLogger('/errors');
}