How To Sort An Array With Null Values

There are quite a few question related to the topic, but I couldn't find the right solution for my case. var arr = [a, b, null, d, null] and am sorting this Array with below logic

Solution 1:

functiongetSort (ascending) {
  // if ascending, `null` will be pushed towards the end of the array by returning 1var nullPosition = ascending ? 1 : -1returnfunction (a, b) {
    // if a is null, push it towards whichever end null elements should end upif (a == null) return nullPosition
    
    // Note: at this point, a is non-null (previous if statement handled that case).//// If b is null, it must therefore be placed closer to whichever end the null// elements should end up on. If ascending, null elements are pulled towards// the right end of the array. If descending, null elements are pulled towards// the left.//// Therefore, we return -nullPosition. If ascending, this is -1, meaning a comes// before b; if descending, this is 1, meaning a comes after b. This is// clearly the correct behavior, since ascending will push b, which is null,// towards the end of the array (with -1) and descending will push b towards// the beginning of the array.if (b == null) return -nullPosition

    // OTHERWISE, both elements are non-null, so sort normally.// if a < b AND//     if ascending, a comes first, so return -1 == -nullPosition//     if descending, a comes after, so return -nullPosition == -(-1) == 1if (a < b) return -nullPosition

    // return the opposite of the previous conditionif (a > b) return nullPosition
    
    // return 0 if both elements are equalreturn0
  }
}

functionwrite (arr) { arr.forEach(function (d) { document.write(d + "<br>")})}

var toSort = ['a', 'b', null, 'd', null]

var sortA = getSort(true)
var sortD = getSort(false)

document.write("<br>ASCENDING<br>")
write(toSort.sort(sortA))

document.write("<br>DESCENDING<br>")
write(toSort.sort(sortD))

Solution 2:

You could use a two pass approach by checking null values first and then order by string.

To change the sort order, you could swap the parameters or use a negated result of the one of the function.

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

// ascending
data.sort(function (a, b) {
    return (a === null) - (b === null) || ('' + a).localeCompare(b);
});
console.log(data);

// descending
data.sort(function (a, b) {
    return (b === null) - (a === null) || ('' + b).localeCompare(a);
});
console.log(data);

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

Solution 3:

What about the below solution?

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

functionsortBy(arr, ascending) {
    return arr.sort((a, b) => {
        if(!a) return ascending ? 1 : -1;
        if(!b) return ascending ? -1 : 1;
        if (ascending) return a > b ? 1 : -1;
        return a > b ? -1 : 1;
    })
}

const ascendingArr = sortBy(arr, true);
console.log(ascendingArr);
const decendingArr = sortBy(arr, false);
console.log(decendingArr);