Extending $log to log to database in AngularJS

$log is a very useful built-in service that is part of the AngularJS (angular 1) distribution. It is even more useful if you could write logs to a database table rather than just to console.

Here’s how you can do it:

Assumes you have a RESTful back-end that responds to the url in the log() function of LoggingService below,


var app = angular.module('app');

app.factory("LoggingService", function ($http) {
    var _isEnabled = true;

    var isEnabled = function () {
        return _isEnabled;
    }

    var enable = function (b) {
        _isEnabled = b;
    }

    var log = function () {
        var url = "/Api/Audit/Log";
        if (this.isEnabled()) {
            var type = "UNK"; // placeholder for when no type is passed
            args = [];
            if (typeof arguments === 'object') {
                type = arguments[0];
                for (var i = 1; i < arguments.length; i++) {
                    arg = arguments[i];
                    if (typeof (arg) != 'string') arg = JSON.stringify(arg);
                    args.push(arg);
                }
                return $http.post(url, { "ACTIVITY": type + ': ' + args.join('\n') });
            }
            else {
                return $http.post(url, { "ACTIVITY": type + ': ' + arguments[0] });
            }
        }
    };

    return {
        log: log,
        enable: enable,
        isEnabled: isEnabled
    };
})

.config(function ($routeProvider, $logProvider, $httpProvider, $provide) {

    $logProvider.debugEnabled(1);

    // -----------------------------------------------------------------------------------
    // logging algorithm suggested by:
    // http://stackoverflow.com/questions/32365811/decorate-angulars-log-to-use-a-service-that-uses-http
    // -----------------------------------------------------------------------------------

    $provide.decorator("$log", function ($delegate, $injector) {

        var logFn = $delegate.log;

        // N.B. Don't delegate $log.debug()...that is ALWAYS written just to the console!
        // $log.warn(), $log.error() and $log.info() are written to both console (assuming $logProvider.debugEnabled == 1) and database
        // $log.db() is written ONLY to database!!

        $delegate.warn = function (message) {
            var LoggingService = $injector.get('LoggingService');
            LoggingService.log('WARN', message);
            if ($logProvider.debugEnabled()) logFn.apply(null, arguments);
        };
        $delegate.error = function (message) {
            var LoggingService = $injector.get('LoggingService');
            LoggingService.log('ERROR', message);
            if ($logProvider.debugEnabled()) logFn.apply(null, arguments);
        };
        $delegate.info = function (message) {
            var LoggingService = $injector.get('LoggingService');
            LoggingService.log('INFO', message);
            if ($logProvider.debugEnabled()) logFn.apply(null, arguments);
        };
        $delegate.db = function (message) {
            var LoggingService = $injector.get('LoggingService');
            LoggingService.log('DB', message);
            // N.B. $log.db is not written to console ever!!
        };
        //Return the delegate
        return $delegate;
    });
//   :
//   :
// more config functionality here
//   :
//   :
}) // end of config function

.run();