CODEWITHSUNDEEP
javascriptsorting
Andrew
Andrew

Reputation: 1150

Sort a JS numerical array in specific order

I have an array [1, 85, -1, -1, 25, 0]

I need it sorted like this: [0, 1, 25, 85, -1, -1]

Tried to use the sort() method but having no luck as its not in ASC order...

Logic: The values represent days from last order. -1 represents no order. Require it ordered by most recent ordered.

Upvotes: 0

Views: 82

Answers (3)

Rahul Bhobe
Rahul Bhobe

Reputation: 4451

You could sort() as usual and then explicitly move the -1s to the end using splice() and push().

let arr = [1, 85, -1, -1, 25, 0];
arr.sort((a, b) => a - b);
let idx = arr.findIndex(a => a != -1);
arr.push(...arr.splice(0, idx));
console.log(arr);

Upvotes: 1

T.J. Crowder
T.J. Crowder

Reputation: 1074008

In the sort callback, you receive two arguments (I usually call them a and b). You return a negative number if a should come before b, 0 if it doesn't matter (they're the same for sorting purposes), or a positive number if a should go after b.

In your case, since -1 goes at the end (you've said there are no other negative numbers), you just need to special-case it:

array.sort((a, b) => {
    if (a === -1) { // < 0 would also work, since there aren't any others
        return 1;
    }
    if (b === -1) { // "
        return -1;
    }
    return a- b;
});

Live Example:

const array = [1, 85, -1, -1, 25, 0];
array.sort((a, b) => {
    if (a === -1) {
        return 1;
    }
    if (b === -1) {
        return -1;
    }
    return a- b;
});
console.log(array);

That can be more concise, of course, I wrote it as above primarily for maximum clarity. But for instance:

array.sort((a, b) => a === -1 ? 1 : b === -1 ? -1 : a - b);

Personally I prefer slightly more verbose than that. But... :-)

Upvotes: 3

Nina Scholz
Nina Scholz

Reputation: 386530

You could check if smaller than zero and sort the rest ascending.

var array = [1, 85, -1, -1, 25, 0];

array.sort((a, b) => (a < 0) - (b < 0) || a - b);

console.log(array);

Upvotes: 2

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