javascript - Sort an array so that null values always come last

Question

I need to sort an array of strings, but I need it so that null is always last. For example, the array:

var arr = [a, b, null, d, null]

When sorted ascending I need it to be sorted like [a, b, d, null, null] and when sorted descending I need it to be sorted like [d, b, a, null, null].

Is this possible? I tried the solution found below but it's not quite what I need.

How can one compare string and numeric values (respecting negative values, with null always last)?

Answer 1

Check out .sort() and do it with custom sorting. Example

function alphabetically(ascending) {

  return function (a, b) {

    // equal items sort equally
    if (a === b) {
        return 0;
    }
    // nulls sort after anything else
    else if (a === null) {
        return 1;
    }
    else if (b === null) {
        return -1;
    }
    // otherwise, if we're ascending, lowest sorts first
    else if (ascending) {
        return a < b ? -1 : 1;
    }
    // if descending, highest sorts first
    else { 
        return a < b ? 1 : -1;
    }

  };

}

var arr = [null, 'a', 'b', null, 'd'];

console.log(arr.sort(alphabetically(true)));
console.log(arr.sort(alphabetically(false)));