Remove array item « Life is grand

Remove array item

I like the way you can add methods/functions/members to built in JavaScript entities. The following adds a remove method to the Array object.

Array.prototype.remove = function(item_to_remove)
{
  for (var i = 0; i < this.length; i++)
  {
    if (this[i] == item_to_remove)
    {
      this.splice(i,1);
      break;
    }
  }
}

Anybody know a better way of removing items from an array?

This entry was posted on Thursday, July 13th, 2006 at 10:56 am and is filed under Array, Code, Development, JavaScript, Remove, prototype. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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David Stone 2 years ago 1 point
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I'd tend to say that using the Array.filter method would be a cleaner way of doing it...but filter doesn't change the actual array, so you couldn't use that.

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Paul Watson 2 years ago 1 point
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hhmm didn't know about Array.filter. Seems quite nice, though I wonder about performance?

And I reckon it could be used, just use this = this.filter(func);.

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David Stone 2 years ago 1 point
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You'd think...but setting this = this.filter... actually results in an error because you're not allowed to re-assign to this.

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Paul Watson 2 years ago 1 point
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Ah yeah, damn, invalid assignment. Hmmmm... So it can be used outside of a prototype extension but not inside. Grr.

Maybe you could do this.clear and then this.push(this.filter blah blah

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David Stone 2 years ago 1 point
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But is that really better than the iteration and the splice?

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David Stone 2 years ago 1 point
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Here. This:

Array.prototype.remove = function(item_to_remove)
{
var index;
while((index = this.indexOf(item_to_remove)) != -1)
{
this.splice(index, 1);
}
}

That'll remove all of the items that match. For instance:

var filtered = [1, 2, 3, 4, 5, 6, 5, 7, 8, 5, 9, 10];
filtered.remove(5);
document.write(filtered);

1,2,3,4,6,7,8,9,10

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David Stone 2 years ago 1 point
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Better:

Array.prototype.remove = function(item_to_remove)
{
var index;
while((index = this.indexOf(item_to_remove)) != -1)
{
this.splice(index, 1);
}
return this;
}

That way you can do:

var filtered = [1, 2, 3, 4, 5, 6, 5, 7, 8, 5, 9, 10].remove(5);
document.write(filtered);

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Andrew Peace 2 years ago 1 point
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The filter operation is quite cool - Python has something identical.

I'm not sure if javascript also has them, but a couple of other useful Python functions on sequences are map and reduce, which behave like:

def map(fn, list):
newlist = []
for item in list:
newlist.append = fn(item)

def reduce(fn ,list, initial_arg = None):
if initial_arg:
val = initial_arg
start = 0
else:
val = list[0]
start = 1

for i in range(start, len(list)):
val = fn(val, myseq[i])
return val

I may have goofed these up as I did them off the top of my head, but hopefully you get the idea.

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Andrew Peace 2 years ago 1 point
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Eek, that didn't look so good - not sure how to get in this message board.

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David Stone 2 years ago 1 point
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Andrew: Here's the JS Array Object documentation that lists what functions Array does have. As you can see, map is in there. And I think reduce is kinda like every: http://developer.mozilla.org/en/docs/Core_JavaS...

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Paul Watson 2 years ago 1 point
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And if it doesn't have it, prototype it :)

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