Why this function is always returning null

Question

This is my JavaScript function to check if a particular entry exists or not in an array, but this is always returning null even though there is a match

function getSupplierForId(supplierId) {                               
    data.suppliers.forEach(x => {                                     
        console.log('Current item id : ' + x.id);                     
        console.log('Requested supplier id : ' + supplierId);         
        console.log('Both ids are equal : ' + (x.id === supplierId)); 
        if (x.id === supplierId) {                                    
            console.log(x);                                           
            return x;                                                 
        }                        
    });                                                               
    return null;                                                      
}

This is my console output:

Why is it returning null always?

Because you have `return null;` at the end. `return` statements do not cross function boundaries. — Felix Kling, Mar 04 '20 at 19:41
What change should i make inorder to return the match without returning null — Sony, Mar 04 '20 at 19:43
Good explanation: https://medium.com/@JeffLombardJr/understanding-foreach-map-filter-and-find-in-javascript-f91da93b9f2c — Darius, Mar 04 '20 at 19:43

score 5 · Accepted Answer · answered Mar 04 '20 at 19:43

Because you have return null; at the end. return statements do not cross function boundaries. return x; only returns from the inner function (whose caller is .forEach), not from the outer function.

Anyways, the right tool to use in your case is .find:

function getSupplierForId(supplierId) {                               
  return data.suppliers.find(x => x.id === supplierId)  
}

You might also find my post about callbacks interesting: https://felix-kling.de/blog/2019/javascript-callbacks-misconceptions.html

Why this function is always returning null

1 Answers1