Javascript "class" (Logger) to use in MongoDB scripts. This class prints the messages (respecting log level specified on constructor).

logger.js

/**
 * Logger class to print messages according to specified level.
 * 
 * Usage:
 * var log = new Logger(Logger.INFO);
 * log.info("Show message");
 */

function Logger(level) {
    this.level = level || Logger.DEBUG;
}

(function () {
    fn = Logger.prototype;

    /* Log levels */
    fn.DEBUG = 10;
    fn.INFO = 20;
    fn.WARNING = 30;
    fn.ERROR = 40;

    fn.LEVEL_NAMES = {};
    fn.LEVEL_NAMES[fn.DEBUG] = 'DEBUG';
    fn.LEVEL_NAMES[fn.INFO] = 'INFO';
    fn.LEVEL_NAMES[fn.WARNING] = 'WARNING';
    fn.LEVEL_NAMES[fn.ERROR] = 'ERROR';

    fn.log = function(level, msg) {
        if (level > this.level) {
            return;
        }

        var levelName = fn.LEVEL_NAMES[level],
            dateFull = ISODate().tojson(),
            dateString = dateFull.replace('ISODate("', '').replace('")', '');
        print(levelName + " " + dateString + " " + msg);
    };

    fn.debug = function(msg) {
        this.log(fn.DEBUG, msg);
    };

    fn.info = function(msg) {
        this.log(fn.INFO, msg);
    };

    fn.warning = fn.warn = function(msg) {
        this.log(fn.WARNING, msg);
    };

    fn.error = function(msg) {
        this.log(fn.ERROR, msg);
    };
}());

usage.js

// Usage example for Logger javascript class
// Don't forget to include the logger.js file

var log = new Logger(Logger.INFO);
log.info("This message will be printed on stdout");
log.error("And so this one");
log.debug("But this don't! (As Logger.INFO was specified on object creation.)");