Node.js process.setUncaughtExceptionCaptureCallback() Method

Last Updated : 28 Apr, 2025

The process.setUncaughtExceptionCaptureCallback() method is an inbuilt application programming interface of the processing module which is used to set a callback function which will be called when an Uncaught Exception occurs. The callback function will receive the exception value as its first argument.

Syntax:

process.setUncaughtExceptionCaptureCallback( callback_function )

Parameters: This method accepts a single parameter as mentioned above and described below.

callback_function: This is a required parameter. It can be a function or null value. If it set to null, then the function will unset the callback function.

Return: It does not return any value.

Below examples illustrate the use of process.setUncaughtExceptionCaptureCallback() method in Node.js:

Example 1:

JavaScript

// Allocating process module
const process = require('process');

// Function to be set as call back
function to_be_called(ex){
    console.log(ex);
}

// Checking whether any callback has been set before calling 
// process.setUncaughtExceptionCaptureCallback(to_be_called);
console.log(process.hasUncaughtExceptionCaptureCallback());

// Setting callback 
process.setUncaughtExceptionCaptureCallback(to_be_called);

// Checking whether any callback has been set before calling 
// process.setUncaughtExceptionCaptureCallback(to_be_called);
console.log(process.hasUncaughtExceptionCaptureCallback());

Output:

false
true

Example 2:

JavaScript

// Allocating process module
const process = require('process');

// Function to be set as call back
function to_be_called(ex) {
    console.log(ex);
}

// Checking whether any callback has been set before calling 
// process.setUncaughtExceptionCaptureCallback(to_be_called);
// Printing whether a callback is set or not
if (process.hasUncaughtExceptionCaptureCallback()) {
    console.log("a callback has been set using " +
        "process.setUncaughtExceptionCaptureCallback() method");
} else {
    console.log("no callback has been set using " +
        "process.setUncaughtExceptionCaptureCallback() method");
}


// Setting callback 
if (process.setUncaughtExceptionCaptureCallback) {
    process.setUncaughtExceptionCaptureCallback(to_be_called);
} else {
    console.log("process.setUncaughtExceptionCaptureCallback() "
        + "method is not defined!");
}

// Checking whether any callback has been set before calling 
// process.setUncaughtExceptionCaptureCallback(to_be_called);
if (process.hasUncaughtExceptionCaptureCallback()) {
    console.log("a callback has been set using " +
        "process.setUncaughtExceptionCaptureCallback() method");
} else {
    console.log("no callback has been set using " +
        "process.setUncaughtExceptionCaptureCallback() method");
}


// Resetting callback 
if (process.setUncaughtExceptionCaptureCallback) {
    process.setUncaughtExceptionCaptureCallback(null);
} else {
    console.log("process.setUncaughtExceptionCaptureCallback() "
        + " method is not defined!");
}

// Checking whether any callback has been set after resetting
if (process.hasUncaughtExceptionCaptureCallback()) {
    console.log("a callback has been set using " +
        "process.setUncaughtExceptionCaptureCallback() method");
} else {
    console.log("no callback has been set using " +
        "process.setUncaughtExceptionCaptureCallback() method");
}

Output:

no callback has been set using process.setUncaughtExceptionCaptureCallback() method
a callback has been set using process.setUncaughtExceptionCaptureCallback() method
no callback has been set using process.setUncaughtExceptionCaptureCallback() method

Note: The above program will compile and run by using the node filename.js command, only in POSIX platforms.

Reference: https://nodejs.org/api/process.html#process_process_setuncaughtexceptioncapturecallback_fn