Knockout sort - null values last

Question

I have an observableArray similar to the below:

self.people = ko.observableArray([
    { firstName: 'Albert', lastName: 'Woods', number: 2 },
    { firstName: 'Barry', lastName: 'Vincent', number: 4 },
    { firstName: 'Jason', lastName: 'Xavier', number: null },
    { firstName: 'Dean', lastName: 'Zebekiah', number: 1 },
    { firstName: 'Marty', lastName: 'Woods', number: 5 },
    { firstName: 'Bill', lastName: 'Vincent', number: 3 },
    { firstName: 'Chris', lastName: 'Jordan', number: null },
    { firstName: 'Ed', lastName: 'Young', number: null },
    { firstName: 'Dave', lastName: 'Zebekiah', number: 5 }
]);

I'm sorting this based on two values - number , which isn't unique, then lastname (I understand this can be written in shorthand, I'm just doing it like this for now for readability):

self.people.sort(function (a, b) {
    if (a.number == b.number) {
        if (a.lastName < b.lastName) {
            return -1;
        } else if (a.lastName > b.lastName) {
            return 1;
        } else {
            return 0;
        }
    } else {
        if (a.number < b.inumberd) {
            return -1;
        } else if (a.number > b.number) {
            return 1;
        } else {
            return 0;
        }
    }
});

This all works fine, except I would like all objects that have a number value of null to be the last items on the list, rather than first. What is the best way to achieve this?

I think I need to do something like the following:

    if (a.number = null){
        return 1;
    }
    if (b.number = null){
        return 0;
    }

But the issue with this is that it no longer uses lastName as the secondary sort term for the relevant objects.

Here is a jsfiddle for reference: http://jsfiddle.net/nimaek/7tsfdfxq/

Thanks.

Answer 1

Try this in your fiddle:

if (a.number == null && b.number){
    return 1;
}
if (b.number == null && a.number){
    return -1;
}

If a.number == null and b.number == null it will compare names. If only one of them is null it will move them down in the list.