Comparing and copying arrays in JavaScript is a pain

Ever wanted to copy an array in JavaScript? Tried the simple var array2 = array1?
Yes, it doesn't work that way.

Apparently with arrays and objects, JS uses references just like C# and in case you want to make a copy of an array...

function CopyArray(a)
{
  //Create a new array with the old ones length
  var n = new Array(a.length);

  //Just copy all the values from the old to the new
  for(var i = 0; i < a.length; i++)
    n[i] = a[i];
  
  return n;
}

var array2 = CopyArray(array1);

You'll have to use something like that. Of course it gets way more complicated when dealing with jagged arrays, eg. arrays which have arrays in them. You'll have to write a recursive function or something the like of this:

function CopyArray(a)
{
  //Create a new array with the old ones length
  var n = new Array(a.length);

  //Just copy all the values from the old to the new
  for(var i = 0; i < a.length; i++)
  {
    //if the value in the old array is an object (array)
    //call the CopyArray function recursively
    if(typeof a[i] == 'object')
      n[i] = CopyArray(a[i]);
    else
      n[i] = a[i];
  }
  
  return n;
}

With that you can create nice copies of arrays while still keeping them as array objects.


How about comparing arrays? Uh oh, if(a == b) doesn't work like expected!

Yet again we'll have to use a customized function

//Check if two arrays' contents are the same
//returns true if they are, otherwise false
Equals = function(a,b)
{
  //Check if the arrays are undefined/null
  if(!a || !b)
    return false;

  //first compare their lengths
  if(a.length == b.length)
  {
    //go thru all the vars
    for(var i = 0; i < a.length;i++)
    {
      //if the var is an array, we need to make a recursive check
      //otherwise we'll just compare the values
      if(typeof a[i] == 'object') {
        if(!Equals(a[i],b[i]))
          return false;
      }
      else if(a[i] != b[i])
        return false;
    }
    return true;
  }
  else return false;
}

if(Equals(a,b)) { /* ... */ }

ookay!

You might notice that the usual JavaScript naming convention is that function names start with a small letter. I use capital letters just because I'm used to that from C# and it looks better to my eye.