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Node.js – util.debuglog() Method
The util.debuglog() method creates a function that can be used to write the desired error/debug messages to stderr. These error messages are written only upon the existence of the NODE_DEBUG environment variable.
Syntax
util.debuglog(section, [callback])
Parameters
The parameters are described below −
section − This parameter takes the portion of the application for which the debug log is being created.
callback − This is the callback function which will receive the pointer if any error occurs during the execution of method.
Example 1
Create a file with the name "debuglog.js" and copy the following code snippet -
// util.debuglog() demo example
// Importing the util module
const util = require('util');
const debugLog = util.debuglog('application#1');
// Use debuglog() method
debugLog('Welcome to Tutorials Point');
let debug = util.debuglog('application#2',
(debuging) => {
// Replace with a logging function
// that optimizes out
a = "new Value";
// Testing if the section is enabled
debug = debuging;
});
// prints the debuglog function
console.log(util.inspect(debug,
showHidden = true, compact = true));
// logs app *
debug();
debug('Hello User #[%d]', 2);Use this following command to run the above application in debug mode -
NODE_DEBUG=application* node debuglog.js
Output
C:\home
ode>> NODE_DEBUG=application* node debuglog.js APPLICATION#1 337356: Welcome to Tutorials Point { [Function: debug] [length]: 0, [name]: 'debug', [prototype]: debug { [constructor]: [Circular] } } APPLICATION#2 337356: APPLICATION#2 337356: Hello User #[2]
Example 2
Let’s have a look at one more example -
// util.debuglog() demo example
// Importing the util module
const util = require('util');
const debuglog = util.debuglog('application');
debuglog('Hello [%s], - From Tutorials Point', 'user');
const generalLog = util.debuglog('app-');
const timerLog = util.debuglog('appl');
const delay = 200;
// Printing the log for 'app-'
generalLog('Exiting app-');
console.log("Waiting for Timer Log to get executed")
// Timer will run after 200 ms
setTimeout(() => {
timerLog('Timer is fired after %d ', delay);
}, delay);Output
C:\home
ode>> NODE_DEBUG=application* node debuglog.js APPLICATION 338111: Hello [user], - From Tutorials Point APP- 338111: Exiting appWaiting for Timer Log to get executed APPL 338111: Timer is fired after 200
Updated on: 18-Aug-2021
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