Javascript - passing variables with an array

Question

I'm working with some code I've adapted from and there's something I don't quite understand the best way to do. I'm trying to streamline a bit of code with different sorting functions that are applying sorts for specific values to an array of list items.

At the moment the function does a compare based on a specific factor and then returns the values to sort.

I want to pass two additional variables with this array/sort call but I can't seem to work out the way to write this. At the moment I'm doing it in a nasty way by having global variables on the window, but I'd rather pass the variables directly.

Based on the code below, any ways to tighten & clean it up would be appreciated:

arr = [];
sort_func = $j(this).children(':selected').val();

$j('li.collectionItem').each(function(){
    arr.push(this);
});

if (sort_func == "a_z")
{
      window.dataType = 'alpha';
      window.bigFirst = false;
      arr.sort(sort_products);
}
else if (sort_func == "z_a")
{
      window.dataType = 'alpha';
      window.bigFirst = true;
      arr.sort(sort_products);
}


// custom sort functions
function sort_products(a, b)
{
  dataType = window.dataType;
  bigFirst = window.bigFirst;

  var compA = $j(a).data(dataType);
  var compB = $j(b).data(dataType);

  if (bigFirst == true)
  {
    return (compA > compB) ? -1 : (compA < compB ) ? 1 : 0;
  }
  else
  {
    return (compA < compB) ? -1 : (compA > compB ) ? 1 : 0;
  }
}

Andrey Kuzmin · Accepted Answer · 2013-08-26 15:41:33Z

1

You can wrap original sort_products in another function, like this:

function sort_products(dataType, bigFirst)
{
  return function (a, b)
  {
    var compA = $j(a).data(dataType);
    var compB = $j(b).data(dataType);

    if (bigFirst == true)
    {
      return (compA > compB) ? -1 : (compA < compB ) ? 1 : 0;
    }
    else
    {
      return (compA < compB) ? -1 : (compA > compB ) ? 1 : 0;
    }
  }
}

And then you can use it like this:

if (sort_func == "a_z")
{
  arr.sort(sort_products('alpha', false));
}
else if (sort_func == "z_a")
{
  arr.sort(sort_products('alpha', true));
}

answered Aug 26, 2013 at 15:41

Andrey Kuzmin

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Comments

Pointy · Accepted Answer · 2013-08-26 15:50:26Z

1

I don't know how many elements you have, but it'd speed things up if you'd avoid making those jQuery (assuming that's what $j is) calls inside the comparator function.

var arr = []; // You really need to declare your variables!
var sort_func = $j(this).children(':selected').val();
var sortInfo = {
  'a_z': {type: 'alpha', ascending: true},
  'z_a': {type: 'alpha', ascending: false},
  // ... whatever the other types are
}[sort_func];

$j('li.collectionItem').each(function(){
  arr.push({ elem: this, key: $j(this).data(sortInfo.type) });
});

arr.sort(function(a, b) {
  return (sortInfo.ascending ? 1 : -1) *
    a.key > b.key ? 1 : a.key < b.key ? -1 : 0;
});

// transform the array into an array of just the DOM nodes
for (var i = 0; i < arr.length; ++i)
  arr[i] = arr[i].elem;

answered Aug 26, 2013 at 15:50

Pointy

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2 Comments

Steve de Niese Over a year ago

Thanks mate, good stuff in here. Agreed on scoping variables. Out of interest is this a speed or compliance issue?

Pointy Over a year ago

@LetterAfterZ well it's mostly performance. The comparison routine will be called a large number of times, so making it as cheap as possible makes a difference for larger lists.

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