建立 node log 系統

最簡單的方式寫下 log

var fs = require('fs');
var util = require('util');
var log_file = fs.createWriteStream(__dirname + '/debug.log', {flags: 'w'});
var log2file = function (v) {
    log_file.write(util.format(v) + '\n');
};

let aa={a:123, b:456};
log2file(aa);

Winston 套件

const winston = require("winston");

const logger = winston.createLogger({
    level: "info",
    format: winston.format.json(),
    transports: [
        new winston.transports.File({
            filename: "logs/files.log",
        }),
    ],
});

logger.log({
    message: "This is a message with Info log level !",
    level: "info",
});

https://www.delftstack.com/zh-tw/howto/node.js/logging-in-node-js/

https://ithelp.ithome.com.tw/articles/10255101

log4js

它的 log 我各人是比較喜歡的

const log4js = require("log4js");
log4js.configure({
    appenders: { cheese: { type: "file", filename: "cheese.log" } },
    categories: { default: { appenders: ["cheese"], level: "error" } },
});

const logger = log4js.getLogger("cheese");
logger.trace("Entering cheese testing");
logger.debug("Got cheese.");
logger.info("Cheese is Comté.");
logger.warn("Cheese is quite smelly.");
logger.error("Cheese is too ripe!");
logger.fatal("Cheese was breeding ground for listeria.");

可以建立 logs 的 folder

log4js.configure({
    appenders: {
        multi: {
            type: "multiFile",
            base: "logs/",
            property: "categoryName",
            extension: ".log",
        },
    },
    categories: {
        default: { appenders: ["multi"], level: "debug" },
    },
});

const logger = log4js.getLogger();
logger.debug("I will be logged in logs/default.log");
const otherLogger = log4js.getLogger("cheese");
otherLogger.info("Cheese is cheddar - this will be logged in logs/cheese.log");

也可以不類 categories

log4js​

log4js