How to temporarily disable log4js logging in javascript?

Question

There are a few third party libraries that are using log4js to output their logs. I know it sounds counter-intuitive but I would like to disable these logs temporarily to be able to investigate an issue that I have.

How do I temporarily disable log4js logs temporarily in code in javascript? Specifically nodejs.

Answer 1

In the app.js file of my nodejs application I place the following code to temporarily disable log4js logs from thirdparty libraries.

const log4js = require('log4js')
log4js.configure({})

This works for disabling the logs.

Answer 2

In log4js 5.3.0 (not sure how many versions back it's the same) you can do this by turning everything off temporarily at the root logger, which affects every other logger:

log4js.getLogger().level = 'off';

A full example:

#!/bin/env node

const log4js = require('log4js');

log4js.configure({
    appenders: {
        out: { type: "stdout" }
    },
    categories: {
        default: {
            appenders: [ "out" ],
            level: "info"
        }
    }
});

const rootLogger = log4js.getLogger();

const log = log4js.getLogger('foo');

log.info('this is on - turning off');

rootLogger.level = 'off';

log.info('this is off - turning back on');

rootLogger.level = 'info';

log.info('this is back on');

Which gives you:

[2019-11-13T22:00:37.541] [INFO] foo - this is on - turning off
[2019-11-13T22:00:37.544] [INFO] foo - this is back on