@std/log@0.212.0

import * as log from "@std/log";

// Simple default logger out of the box. You can customize it
// by overriding logger and handler named "default", or providing
// additional logger configurations. You can log any data type.
log.debug("Hello world");
log.info(123456);
log.warn(true);
log.error({ foo: "bar", fizz: "bazz" });
log.critical("500 Internal server error");

// custom configuration with 2 loggers (the default and `tasks` loggers).
log.setup({
  handlers: {
    console: new log.handlers.ConsoleHandler("DEBUG"),

    file: new log.handlers.FileHandler("WARNING", {
      filename: "./log.txt",
      // you can change format of output message using any keys in `LogRecord`.
      formatter: (record) => `${record.levelName} ${record.msg}`,
    }),
  },

  loggers: {
    // configure default logger available via short-hand methods above.
    default: {
      level: "DEBUG",
      handlers: ["console", "file"],
    },

    tasks: {
      level: "ERROR",
      handlers: ["console"],
    },
  },
});

let logger;

// get default logger.
logger = log.getLogger();
logger.debug("fizz"); // logs to `console`, because `file` handler requires "WARNING" level.
logger.warn(41256); // logs to both `console` and `file` handlers.

// get custom logger
logger = log.getLogger("tasks");
logger.debug("fizz"); // won't get output because this logger has "ERROR" level.
logger.error({ productType: "book", value: "126.11" }); // log to `console`.

// if you try to use a logger that hasn't been configured
// you're good to go, it gets created automatically with level set to 0
// so no message is logged.
const unknownLogger = log.getLogger("mystery");
unknownLogger.info("foobar"); // no-op

import * as log from "@std/log";

log.setup({
  handlers: {
    stringFmt: new log.handlers.ConsoleHandler("DEBUG", {
      formatter: (record) => `[${record.levelName}] ${record.msg}`,
    }),

    functionFmt: new log.handlers.ConsoleHandler("DEBUG", {
      formatter: (logRecord) => {
        let msg = `${logRecord.level} ${logRecord.msg}`;

        logRecord.args.forEach((arg, index) => {
          msg += `, arg${index}: ${arg}`;
        });

        return msg;
      },
    }),

    anotherFmt: new log.handlers.ConsoleHandler("DEBUG", {
      formatter: (record) => `[${record.loggerName}] - ${record.levelName} ${record.msg}`,
    }),
  },

  loggers: {
    default: {
      level: "DEBUG",
      handlers: ["stringFmt", "functionFmt"],
    },
    dataLogger: {
      level: "INFO",
      handlers: ["anotherFmt"],
    },
  },
});

// calling:
log.debug("Hello, world!", 1, "two", [3, 4, 5]);
// results in: [DEBUG] Hello, world!
// output from "stringFmt" handler.
// 10 Hello, world!, arg0: 1, arg1: two, arg3: [3, 4, 5] // output from "functionFmt" formatter.

// calling:
log.getLogger("dataLogger").error("oh no!");
// results in:
// [dataLogger] - ERROR oh no! // output from anotherFmt handler.

import * as log from "@std/log";

log.setup({
  handlers: {
    jsonStdout: new log.handlers.ConsoleHandler("DEBUG", {
      formatter: log.formatters.jsonFormatter,
      useColors: false,
    }),
  },

  loggers: {
    default: {
      level: "DEBUG",
      handlers: ["jsonStdout"],
    },
  },
});

// calling:
log.info("Hey");
// results in:
// {"level":"INFO","datetime":1702481922294,"message":"Hey"}

// calling:
log.info("Hey", { product: "nail" });
// results in:
// {"level":"INFO","datetime":1702484111115,"message":"Hey","args":{"product":"nail"}}

// calling:
log.info("Hey", 1, "two", [3, 4, 5]);
// results in:
// {"level":"INFO","datetime":1702481922294,"message":"Hey","args":[1,"two",[3,4,5]]}

import * as log from "@std/log";

log.setup({
  handlers: {
    customJsonFmt: new log.handlers.ConsoleHandler("DEBUG", {
      formatter: (record) => JSON.stringify({
        lvl: record.level,
        msg: record.msg,
        time: record.datetime.toISOString(),
        name: record.loggerName,
      }),
      useColors: false,
    }),
  },

  loggers: {
    default: {
      level: "DEBUG",
      handlers: ["customJsonFmt"],
    },
  },
});

// calling:
log.info("complete");
// results in:
// {"lvl":20,"msg":"complete","time":"2023-12-13T16:38:27.328Z","name":"default"}

import * as logger from "@std/log";

const stringData: string = logger.debug("hello world");
const booleanData: boolean = logger.debug(true, 1, "abc");
const fn = (): number => {
  return 123;
};
const resolvedFunctionData: number = logger.debug(fn());
console.log(stringData); // 'hello world'
console.log(booleanData); // true
console.log(resolvedFunctionData); // 123

import * as log from "@std/log";

log.setup({
  handlers: {
    console: new log.handlers.ConsoleHandler("DEBUG"),
  },

  loggers: {
    tasks: {
      level: "ERROR",
      handlers: ["console"],
    },
  },
});

function someExpensiveFn(num: number, bool: boolean) {
  // do some expensive computation
}

// not logged, as debug < error.
const data = log.debug(() => someExpensiveFn(5, true));
console.log(data); // undefined