index.d.ts

// Originally from Definitely Typed, see:
// https://github.com/DefinitelyTyped/DefinitelyTyped/blob/b4683d7/types/loglevel/index.d.ts
// Original definitions by: Stefan Profanter <https://github.com/Pro>
//                          Gabor Szmetanko <https://github.com/szmeti>
//                          Christian Rackerseder <https://github.com/screendriver>

declare const log: log.RootLogger;
export = log;

declare namespace log {
    /**
     * Log levels
     */
    interface LogLevel {
        TRACE: 0;
        DEBUG: 1;
        INFO: 2;
        WARN: 3;
        ERROR: 4;
        SILENT: 5;
    }

    /**
     * Possible log level numbers.
     */
    type LogLevelNumbers = LogLevel[keyof LogLevel];

    /**
     * Possible log level descriptors, may be string, lower or upper case, or number.
     */
    type LogLevelDesc = LogLevelNumbers | LogLevelNames | 'silent' | keyof LogLevel;

    type LogLevelNames =
        | 'trace'
        | 'debug'
        | 'info'
        | 'warn'
        | 'error';

    type LoggingMethod = (...message: any[]) => void;

    type MethodFactory = (methodName: LogLevelNames, level: LogLevelNumbers, loggerName: string | symbol) => LoggingMethod;

    interface RootLogger extends Logger {
        /**
         * If you're using another JavaScript library that exposes a 'log' global, you can run into conflicts with loglevel.
         * Similarly to jQuery, you can solve this by putting loglevel into no-conflict mode immediately after it is loaded
         * onto the page. This resets to 'log' global to its value before loglevel was loaded (typically undefined), and
         * returns the loglevel object, which you can then bind to another name yourself.
         */
        noConflict(): any;

        /**
         * This gets you a new logger object that works exactly like the root log object, but can have its level and
         * logging methods set independently. All loggers must have a name (which is a non-empty string or a symbol)
         * Calling * getLogger() multiple times with the same name will return an identical logger object.
         * In large applications, it can be incredibly useful to turn logging on and off for particular modules as you are
         * working with them. Using the getLogger() method lets you create a separate logger for each part of your
         * application with its own logging level. Likewise, for small, independent modules, using a named logger instead
         * of the default root logger allows developers using your module to selectively turn on deep, trace-level logging
         * when trying to debug problems, while logging only errors or silencing logging altogether under normal
         * circumstances.
         * @param name The name of the produced logger
         */
        getLogger(name: string | symbol): Logger;

        /**
         * This will return you the dictionary of all loggers created with getLogger, keyed off of their names.
         */
        getLoggers(): { [name: string]: Logger };

        /**
         * A .default property for ES6 default import compatibility
         */
        default: RootLogger;
    }

    interface Logger {
        /**
         * Available log levels.
         */
        readonly levels: LogLevel;

        /**
         * Plugin API entry point. This will be called for each enabled method each time the level is set
         * (including initially), and should return a MethodFactory to be used for the given log method, at the given level,
         * for a logger with the given name. If you'd like to retain all the reliability and features of loglevel, it's
         * recommended that this wraps the initially provided value of log.methodFactory
         */
        methodFactory: MethodFactory;

        /**
         * Output trace message to console.
         * This will also include a full stack trace
         *
         * @param msg any data to log to the console
         */
        trace(...msg: any[]): void;

        /**
         * Output debug message to console including appropriate icons
         *
         * @param msg any data to log to the console
         */
        debug(...msg: any[]): void;

        /**
         * Output debug message to console including appropriate icons
         *
         * @param msg any data to log to the console
         */
        log(...msg: any[]): void;

        /**
         * Output info message to console including appropriate icons
         *
         * @param msg any data to log to the console
         */
        info(...msg: any[]): void;

        /**
         * Output warn message to console including appropriate icons
         *
         * @param msg any data to log to the console
         */
        warn(...msg: any[]): void;

        /**
         * Output error message to console including appropriate icons
         *
         * @param msg any data to log to the console
         */
        error(...msg: any[]): void;

        /**
         * This disables all logging below the given level, so that after a log.setLevel("warn") call log.warn("something")
         * or log.error("something") will output messages, but log.info("something") will not.
         *
         * @param level as a string, like 'error' (case-insensitive) or as a number from 0 to 5 (or as log.levels. values)
         * @param persist Where possible the log level will be persisted. LocalStorage will be used if available, falling
         *     back to cookies if not. If neither is available in the current environment (i.e. in Node), or if you pass
         *     false as the optional 'persist' second argument, persistence will be skipped.
         */
        setLevel(level: LogLevelDesc, persist?: boolean): void;

        /**
         * Returns the current logging level, as a value from LogLevel.
         * It's very unlikely you'll need to use this for normal application logging; it's provided partly to help plugin
         * development, and partly to let you optimize logging code as below, where debug data is only generated if the
         * level is set such that it'll actually be logged. This probably doesn't affect you, unless you've run profiling
         * on your code and you have hard numbers telling you that your log data generation is a real performance problem.
         */
        getLevel(): LogLevel[keyof LogLevel];

        /**
         * This sets the current log level only if one has not been persisted and can’t be loaded. This is useful when
         * initializing scripts; if a developer or user has previously called setLevel(), this won’t alter their settings.
         * For example, your application might set the log level to error in a production environment, but when debugging
         * an issue, you might call setLevel("trace") on the console to see all the logs. If that error setting was set
         * using setDefaultLevel(), it will still say as trace on subsequent page loads and refreshes instead of resetting
         * to error.
         *
         * The level argument takes is the same values that you might pass to setLevel(). Levels set using
         * setDefaultLevel() never persist to subsequent page loads.
         *
         * @param level as a string, like 'error' (case-insensitive) or as a number from 0 to 5 (or as log.levels. values)
         */
        setDefaultLevel(level: LogLevelDesc): void;

        /**
         * This resets the current log level to the default level (or `warn` if no explicit default was set) and clears
         * the persisted level if one was previously persisted.
         */
        resetLevel(): void;

        /**
         * This enables all log messages, and is equivalent to log.setLevel("trace").
         *
         * @param persist Where possible the log level will be persisted. LocalStorage will be used if available, falling
         *     back to cookies if not. If neither is available in the current environment (i.e. in Node), or if you pass
         *     false as the optional 'persist' second argument, persistence will be skipped.
         */
        enableAll(persist?: boolean): void;

        /**
         * This disables all log messages, and is equivalent to log.setLevel("silent").
         *
         * @param persist Where possible the log level will be persisted. LocalStorage will be used if available, falling
         *     back to cookies if not. If neither is available in the current environment (i.e. in Node), or if you pass
         *     false as the optional 'persist' second argument, persistence will be skipped.
         */
        disableAll(persist?: boolean): void;

        /**
         * Rebuild the logging methods on this logger and its child loggers.
         *
         * This is mostly intended for plugin developers, but can be useful if you update a logger's `methodFactory` or
         * if you want to apply the root logger’s level to any *pre-existing* child loggers (this updates the level on
         * any child logger that hasn't used `setLevel()` or `setDefaultLevel()`).
         */
        rebuild(): void;
    }
}