javascript - Use array.pop() twice in a row to get second last element - Stack Overflow

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var path = document.location.pathName;
example/store/order/cats

Sometimes it might be:

example/store/order/cats/

Note the slash at the end.

I'd like a function to return cats in either case. If there is no trailing slash I go:

function() {
    return path.split('/').pop();
}

But if there is a trailing slash, I need to pop() twice. I tried this:

function() {
        return path.split('/').pop().pop();
    }

Which threw an error.

So the array arising from split('/') can be either:

["", "store", "order", "cats", ""] // trailing slash

or

["", "store", "order", "cats"] // no trailing slash

How can I return cats in either eventuality?

var path = document.location.pathName;
example./store/order/cats

Sometimes it might be:

example./store/order/cats/

Note the slash at the end.

I'd like a function to return cats in either case. If there is no trailing slash I go:

function() {
    return path.split('/').pop();
}

But if there is a trailing slash, I need to pop() twice. I tried this:

function() {
        return path.split('/').pop().pop();
    }

Which threw an error.

So the array arising from split('/') can be either:

["", "store", "order", "cats", ""] // trailing slash

or

["", "store", "order", "cats"] // no trailing slash

How can I return cats in either eventuality?

• javascript
• arrays

Share Improve this question Follow edited Sep 19, 2015 at 16:26 Tushar 87.2k2121 gold badges163163 silver badges181181 bronze badges asked Sep 19, 2015 at 13:42 Doug FirDoug Fir 21.3k5454 gold badges191191 silver badges340340 bronze badges

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7 Answers 7

Sorted by: Reset to default 3

As others have said, you could try removing the last character if it is a slash, and then using the first method.

function getLastWordInPathName() {
  var path = document.location.pathName.replace(/\/$/, '');
  return path.split('/').pop();
}

However, your question was asking why you can't call pop() twice.

The first time you call pop(), the value of the last element in the array is returned. When you call pop() again, this function is applied to the result of the previous function - so you are calling pop() on the string '/', and not on your array.

There are indeed many ways to skin a cat. These assume you want one liners rather than something more defensive and that performs well.

If you always want the second from last

[1,2,3,4,5].slice(-2).shift()
4

This will likely perform very slightly better:

[1,2,3,4,5].slice(-2, -1)[0]
4

To extract all non-empty delimited items:

'/a/b//c/d/'.match(/[^\/]+/g)
[a, b, c, d]

You can first remove the last trailing / from the string and then use pop on the resulting string.

var path = document.location.pathName.replace(/\/$/, '');

var pathName = path.split('/').pop();

The regex \/$ will match the trailing / from the string. The / need to escape by preceding with \.

You can also use string methods as follow:

if (path.charAt(path.length - 1) === '/') {
    path = path.substr(0, path.length - 1);
}

This is by far the simplest approach:

// Couldn't resist :)
function getCats( location ) {
    if ( location.charAt( location.length-1 ) == "/" ) {
        location = location.slice(0, -1)
    }

    return location.split("/").pop()
}

Array.pop() returns the last element, not the original Array. So the second pop() is called on the last element. If it does not have pop method, you get an error...

To get the second path element from the end use path.replace(/.*\/([^\/]+)\/([^\/]+)\/?$/,'$1')

As you can see in this JSFiddle http://jsfiddle/zarjay/mbggs/ pop is a lot more efficient than RegExp

Have a look at this bit of code now:

function( ) {
  var paths = path.split( "/" ),
      cats = paths.pop( );

  if( !cats ) {
    cats = paths.pop( );
  }

  return cats;
}

You see after you pop paths the first time, you remove the last element of the array

Now if you find that that element is empty, you just pop again and you get the element you want

Your performance is going to be a lot better and if you ever use this in a loop with thousands of iterations you'll get a performance boost in the order of seconds

And that's neat

You can just iterate and throw away empty path elements at the end:

function pathTail(path) {
  for (var split = path.split("/"), tail = split.pop(); !tail; tail = split.pop());
  return tail;
}

Or you can use a regular expression:

function pathTail(path) {
  return path.replace(/^.*\/([^/]+)\/*$/, "$1");
} 

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