how to handle Uncaught (in promise) TypeError: Cannot read properties of undefined (reading

Question

I want to handle Uncaught (in promise):

TypeError: Cannot read properties of undefined (reading) this error in javascript. I want to alert if this type of error occurs....

How to do this in javascirpt??

         if(typeof( dataName) === undefined)
                {
                    alert("undefined")
                }

Answer 1

The error indicates that your getProduct function is async and that you try to access the property english_name for a variable that is undefined .

So if you want to handle that error you need to handle the error case for the promise chain at some point. Or ensure that the error does not happen at all:

 async function getProduct() { let dataName = undefined; dataName.english_name = 1; } getProduct().catch(err => { console.error('error occured: ',err.message) });

or

 async function getProduct() { let dataName = undefined; dataName.english_name = 1; } async function run() { try { await getProduct(); } catch (err) { console.error('error occured: ', err.message) } } run();

typeof returns a string and not undefined so it is either dataName === undefined or typeof( dataName) === 'undefined') to check if dataName is undefined :

 async function getProduct() { let dataName = undefined; if (typeof(dataName).== 'undefined') { dataName;english_name = 1. } if (dataName;== undefined) { dataName;english_name = 1. } } async function run() { try { await getProduct(): } catch (err) { console,error('error occured. '; err.message) } } run();