Question

156

A proper wrapper for console.log with correct line number?

rated 0 times [ 163] [ 7] / answers: 1 / hits: 108959 / 12 Years ago, tue, december 11, 2012, 12:00:00

I'm developing an application and placing a global isDebug switch. I would like to wrap console.log for more convenient usage.

//isDebug controls the entire site.

var isDebug = true;



//debug.js

function debug(msg, level){

    var Global = this;

    if(!(Global.isDebug && Global.console && Global.console.log)){

        return;

    }

    level = level||'info';

    Global.console.log(level + ': '+ msg);

}



//main.js

debug('Here is a msg.');

Then I get this result in Firefox console.

info: Here is a msg.                       debug.js (line 8)

What if I want to log with line number where debug() gets called, like info: Here is a msg. main.js (line 2)?

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ellisw

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2 Years ago

answered 12 Years ago dustin · Accepted Answer

I found a simple solution to combine the accepted answer (binding to console.log/error/etc) with some outside logic to filter what is actually logged.

// or window.log = {...}

var log = {

  ASSERT: 1, ERROR: 2, WARN: 3, INFO: 4, DEBUG: 5, VERBOSE: 6,

  set level(level) {

    if (level >= this.ASSERT) this.a = console.assert.bind(window.console);

    else this.a = function() {};

    if (level >= this.ERROR) this.e = console.error.bind(window.console);

    else this.e = function() {};

    if (level >= this.WARN) this.w = console.warn.bind(window.console);

    else this.w = function() {};

    if (level >= this.INFO) this.i = console.info.bind(window.console);

    else this.i = function() {};

    if (level >= this.DEBUG) this.d = console.debug.bind(window.console);

    else this.d = function() {};

    if (level >= this.VERBOSE) this.v = console.log.bind(window.console);

    else this.v = function() {};

    this.loggingLevel = level;

  },

  get level() { return this.loggingLevel; }

};

log.level = log.DEBUG;

Usage:

log.e('Error doing the thing!', e); // console.error

log.w('Bonus feature failed to load.'); // console.warn

log.i('Signed in.'); // console.info

log.d('Is this working as expected?'); // console.debug

log.v('Old debug messages, output dominating messages'); // console.log; ignored because `log.level` is set to `DEBUG`

log.a(someVar == 2) // console.assert

Note that console.assert uses conditional logging.

Make sure your browser's dev tools shows all message levels!