javascript sorting array of mixed strings and null values

Question

When soritng an array made of a mix of strings, null values and zeros, i get the result not properly as exptected, null values seem to get sorted as if they were 'null' strings. I did this (tested on FireFox):

var arr1 = arr2 = [null, "b", "c", "d", null, "e", 0, "g", null, 0, "h", "i", "l", "m", "n", "o", "p", "ne", "nur", "nimbus"];

document.write("SORTED ARRAY:<br>");
arr1.sort();
arr1.forEach(function(val){document.write(val + "; ")});

And the result is:

SORTED ARRAY: 0; 0; b; c; d; e; g; h; i; l; m; n; ne; nimbus; null; null; null; nur; o; p;

Do you have an idea of how to make the null value be considered like empty string during the sorting of the array, so that they appear 1st in the sorted arry along with the zeros.

Thanks!

Answer 1

The browser is doing null.toString(); since null is an Object, this is pretty much Object.toString()... which would return "null"

Pass in a parameter to sort, as your comparison function [if the function returns something greater than 0, b is sorted lower than a]

function would basically be:

comparisonFunc = function(a, b)
{
 if((a === null) && (b === null)) return 0; //they're both null and equal
 else if((a === null) && (b != null)) return -1; //move a downwards
 else if((a != null) && (b === null)) return 1; //move b downwards
 else{
  //Lexicographical sorting goes here
 }
}
set.sort(comparisonFunc);

Answer 2

You can pass the sort a sortfunction

array.sort(sortfunction)

where sortfunction does the comparison you need (regular sorting with null values being greater than others)

Answer 3

Use a custom ordering function that handles null values this way.

arr1.sort(function(a, b) {
    if (a===null) a='';
    if (b===null) b='';

    if (''+a < ''+b) return -1;
    if (''+a > ''+b) return  1;

    return 0;
});

Answer 4

This will do what you want by converting everything to strings (in particular converting null to an empty string) and allowing JavaScript's built-in string comparison do the work:

arr2.sort( function(a, b) {
    a = (a === null) ? "" : "" + a;
    b = (b === null) ? "" : "" + b;
    return a > b ? 1 : ( a === b ? 0 : -1 );
} );

Answer 5

[null, "b", "c", "d", null, "e", 0, "g", null, 0, "h", "i", "l", "m", "n", "o", "p", "ne", "nur", "nimbus"].sort(function (a,b) { 
   return a === null ? -1 : b === null ? 1 : a.toString().localeCompare(b);
});