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Node.js – process.emitWarning() Method
The process.emitWarning() method can be used to emit custom or user-defined process warnings. This can be listened by adding a handler to the warning event.
Syntax
process.emitWarning(warning, [options])
Parameters
warning – This is the warning that will be emitted.
options –
type – This is the type of warning being emitted. Default ‘Warning’
code – This is a unique identifier for the warning that will be emitted.
ctor – This is an optional function used to limit the generated stack trace.
detail – This is the additional text to be included with the error.
Example 1
Create a file with the name "warning.js" and copy the following code snippet. After creating the file, use the command "node warning.js" to run this code.
console.log("Start ...");
// Interval set to keep the process running
setInterval(() => {
console.log("Running ...");}, 1000);
setTimeout(() => {
process.emitWarning('An Error occured!', {
code: 'Custom_Warning',
detail: 'Additional information about warning'
});
}, 4000);
// Start listening
process.on('warning', (warning) => {
// Print msg if there is a warning
if (warning) {
console.log(warning);
process.exit(0);
}
});Output
Start ...
Running ...
Running ...
Running ...
{ [object Object]: An Error occured!
at Timeout.setTimeout (/home/cg/root/8008764/main.js:8:12)
at ontimeout (timers.js:386:14)
at tryOnTimeout (timers.js:250:5)
at Timer.listOnTimeout (timers.js:214:5)
name:
{ code: 'Custom_Warning',
detail: 'Additional information about warning' } }
(node:13011) [object Object]: An Error occured!Example 2
Let’s take a look at one more example.
console.log("Start ...");
// Interval set to keep the process running
setInterval(() => {
console.log("Running ...");
}, 1000);
setTimeout(() => {
process.emitWarning('An Error occured!', {
code: 'Custom_Warning',
detail: 'Additional information about warning'
});
}, 2000);
setTimeout(() => {
process.emitWarning('ALERT! WARNING OCCURED', {
type: 'IMPORTANT',
code: '001',
detail: 'Can not proceed further!'
});
}, 4000);
// Start listening
process.on('warning', (warning) => {
// Print msg if there is an Important warning
if (warning.name === 'IMPORTANT') {
console.log('Fix this ASAP!')
process.exit(0);
}
});Output
Start ... Running ... Running ... Running ... Running ... Running ... Running ... Running ... Running ... Running ... (node:18756) [object Object]: An Error occured! (node:18756) [object Object]: ALERT! WARNING OCCURED
Updated on: 29-Oct-2021
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