const str = "Si0m1123on994";
const strAry = str.split('');

Next, we have to Iterate over the array using map() method.

let strRes = strAry.map(function(res){
   
})

Now we have to check if the current element is a number or not using isNaN().

Using the function isNaN(), we are able to return only elements that are not integers.

let strRes = strAry.map(function(res){
    return( (isNaN(res)) ? res : null );
})

Then we convert the result back to string.

let result = strRes.join('');
console.log(result);

Testing out our code

I will use the string above to test my code

Here's an image with the printed value.

It works!

Thank you for reading!