Node.js – util.deprecate() method

Node.jsServer Side ProgrammingProgramming

The util.deprecate() method wraps fn (that may be a function or class) in such a way that it is marketed as a deprecated method. The util.deprecate() method returns a function that emits a DeprecationWarning. This warning is printed to the stderr when the function is called the first time. The function is called without any warning once the warning is emitted.


util.deprecate( fn, msg, [code] )


The parameters are defined below:

  • fn − The function that needs to be deprecated.
  • msg − This is a warning message which is invoked once the deprecated function is called.
  • code − This is an optional parameter which displays the passed code for deprecated function.

Example 1

Create a file named "deprecate.js" and copy the following code snippet. After creating the file, use the command "node deprecate.js" to run this code.

 Live Demo

const util = require('util');
var deprecateFunction = util.deprecate(
   // Defining the deprecated function
   function () { },

   // Msg printed for deprecation
   "Warning: This method is deprecated !",

   // Deprecated API
   'Deprication API'
// Function call


C:\home\node>> node deprecate.js
(node:153883) [Deprication API] DeprecationWarning: Warning: This method is deprecated !

Example 2

 Live Demo

const util = require('util');

function fun() {
   console.log("Welcome to Tutorials Point");

var msg = 'This function is deprecated'
var code = 'DEP0001';
var deprecateFunction = util.deprecate(fun, msg, code);

// Function call


C:\home\node>> node deprecate.js
Welcome to Tutorials Point
(node:157003) [DEP0001] DeprecationWarning: This function is deprecated
Published on 17-Aug-2021 11:14:33