custom array.sort function with several criteria incl. boolean

Question

I have an array of objects that i would like to order by several properties.

Im going to showcase a single element of the array

var ele = {
    id: INT, various,
    priority: INT 1 - 10,
    shooterid: INT various,
    targetid: INT various,
    flight: BOOL
}

i would like to order the array according to some criteria and i can do the sort by priority, shooter and target by using

if (a.priority != b-priority){
  return a-priority - b-priority;
else if a.shooterid != b.shooterid){
  return a.shooterid - b. shooterid
}
else return a.targetid - b.targetid

However, i also want to sort by flight and i would like to all elements with flight = true to be sorted LAST in addition to the above sort.

I tried if (a.flight){return -1/0/1} a the very top of the above if/self (adding else to the formerly if) but it didnt work...

How can i extend the sort to include for the BOOL prop ?

Just make the flight comparison the first thing you do. If the flight properties are different, then nothing else matters. You say that "didn't" work, but it will work; describe what went wrong or else nobody can really help you. — Pointy
– Pointy, Commented Feb 13, 2017 at 14:50
Did you literally the try the code return -1/0/1? That's negative Infinity (negative one divided by zero divided by one) -- is that what you intended? Or do you mean you tried each of those values separately and nothing worked? — apsillers
– apsillers, Commented Feb 13, 2017 at 14:51
You still need to compare the flight like anything else, because if you return any value unconditionally when flight is true then you can’t compare within the list of elements that have flight. — Ry-
– Ry- ♦, Commented Feb 13, 2017 at 14:52

Nina Scholz · Accepted Answer · 2017-05-12 18:12:27Z

You could combine all sort criteria with logical or ||, even the boolean values.

var data = [{ id: 0, flight: true, priority: 1, shooterid: 2, targetid: 1 }, { id: 1, flight: true, priority: 2, shooterid: 2, targetid: 3 }, { id: 2, flight: false, priority: 1, shooterid: 1, targetid: 2 }, { id: 3, flight: false, priority: 2, shooterid: 1, targetid: 1 }, { id: 4, flight: true, priority: 1, shooterid: 1, targetid: 2 }];

data.sort(function (a, b) {
    return (
        a.flight - b.flight ||
        a.priority - b.priority ||
        a.shooterid - b.shooterid ||
        a.targetid - b.targetid
    );
});

console.log(data);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Pointy · Accepted Answer · 2017-02-13 14:54:32Z

1

The first if should be:

if (a.flight != b.flight)
  return a.flight - b.flight;

In the subtraction, boolean true will be treated as 1 and false as 0. That means that the false ones will sort before the true ones, as you say you want.

answered Feb 13, 2017 at 14:54

Pointy

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1 Comment

user431806 Over a year ago

Thanks for your answer. I decided to approve the other answer because it looks clean with || instead of if/else. However, i appreciate your explanation on the reasoning.

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