Question

I’m having issues with javascript array sorting and integers. I have these functions defined:

function sortA(a,b){ 
  return a - b;
}
function sortD(a,b){ 
  return b - a;
}

then in a jquery $.each, I put some content in the arrays:

$('.'+sort_column).each(function(index, value) {

    var current_num = $.trim($(this).text())

    current_num = parseInt(current_num, 10); //convert to integer for numeric sorting.

    valuesArr.push(current_num);  

    console.log(typeof index); //just checking...this shows number in the console
});

var sort_asc = valuesArr.sort(sortA);
var sort_desc = valuesArr.sort(sortD);
console.log(sort_asc);
console.log(sort_desc);

but in the console, I get the arrays in the same order.

//console
[1214500, 1214499, 1214497, 1214481, 1214432, 1214421, 1214419, 1214418, 1214369, 1214045, 1205691]
[1214500, 1214499, 1214497, 1214481, 1214432, 1214421, 1214419, 1214418, 1214369, 1214045, 1205691]

curiously, if I append a string to the end, the sorting works

console.log( valuesArr.sort(sortD)  + "asdf");
console.log( valuesArr.sort(sortA)  + "asdf");

//console
[1214500,1214499,1214497,1214481,1214432,1214421,1214419,1214418,1214369,1214045,1205691asdf] 
[1205691,1214045,1214369,1214418,1214419,1214421,1214432,1214481,1214497,1214499,1214500asdf]

I don’t know why I even tried that, but there you go. This is the first time I’ve worked with this method, so I’ve likely missed something quite basic. Many thanks for any help!

Answer 1

You’re sorting the same array’s instance, that’s why the order is the same. Basically sort changes the content of the array itself.

So both of them will be in desc order (that is the last sorting you’re doing). If you want to keep the original instance intact, you should create new arrays:

var sort_asc = valuesArr.slice(0).sort(sortA);
var sort_desc = valuesArr.slice(0).sort(sortD);

console.log(valuesArr);
console.log(sort_asc);
console.log(sort_desc);

See also slice.