Null Checks for a large hierarchical object in Javascript

Question

We have a large hierarchical object (worst possible legacy design) in javascript. The problem I am facing is that there is a list of null checks I need to perform whenever I want to access an element deep within the object structure.

Say I have a bank object which contains a list of customers and I want to get the address of the first customer,

if(bank != null ||
bank.customerlist != null ||
bank.customerlist.customer[0] != null ||
bank.customerlist.customer[0].address != null )
{

transactionAddress = bank.customerlist.customer[0].address;
}

This is just a small example,I cannot believe so many null checks are required just to access a single value.

It there a better way around this?

Answer 1

You could create your own accesser function:

function access(obj, path) {
    var arr = path.split('/');
    while(obj && arr.length)
        obj = obj[arr.shift()];
    return obj;
}

And use it like this:

var bank = {
    customerlist: {customer: [{address: 'foo'}]}
}
access(bank, 'customerlist/customer/0/address'); // 'foo'
access(bank, 'bar/foo/foobar');                  // undefined (no error)

---

Also consider using...

function access(obj, path) {
    var arr = path.split('/');
    while(obj!=null && arr.length)
        obj = obj[arr.shift()];
    return obj;
}

...if you want to use access with non-objects, e.g. you want access('', 'length') to return 0

---

Explaining,

function access(obj, path) {
    var arr = path.split('/');
    while (
        obj /* To avoid `null` and `undefined`. Also consider `obj != null` */
        && /* Logical AND */
        arr.length /* Check that `arr` still has elements */
    ) {
        obj = obj[arr.shift()]; /* `arr.shift()` extracts the first
                                   element is `arr` */
    }
    return obj;
}