SassyLists 
Here is a powerful toolbox providing you all the functions you need to manipulate your Sass lists. See complete documentation here.
How to use it
Install with Gem
gem install SassyLists
Install with Bower
bower install SassyLists --save-dev
- Import the partial in your Sass files
What's in there?
sl-chunk(): returns whether list contains $value
sl-comma-list(): initializes an empty comma-separated list
sl-contain(): returns whether the list contains the value
sl-count-values(): counts the number of occurrences of each value of list
sl-debug(): returns list as a string
sl-every(): returns whether all items from list pass test from given function
sl-explode(): explodes a string into a list using a string as a delimiter
sl-first(): returns first value in list
sl-flatten(): turns multidimensional list into a one-level list
sl-has-values(): checks if list is not empty
sl-has-multiple-values(): checks if list has more than one value
sl-insert-nth(): inserts value at index
sl-intersection(): returns a list of shared values across all given lists
sl-is-empty(): checks if list is empty
sl-is-single(): checks if list has a single value
sl-is-symmetrical(): checks if list is symmetrical
sl-last(): returns last value in list
sl-last-index(): returns last index of value in list
sl-loop(): shifts indexes in list
sl-prepend(): prepends value to list
sl-purge(): removes all false and null values from list
sl-random-value(): returns random value from list
sl-range(): returns a list of values between 1 and given value
sl-remove(): removes value in list
sl-remove-duplicates(): removes duplicate values from list
sl-remove-nth(): removes value at index
sl-replace(): replaces value in list
sl-replace-nth(): replaces value at index
sl-reverse(): reverses list
sl-shuffle(): shuffles list
sl-slice(): slices list
sl-sort(): sorts list
sl-some(): returns whether some values from list pass test from given function
sl-sum(): sums all unitless values in list
sl-tail(): returns anything but the first element in list
sl-to-list(): casts value as list
sl-to-map(): casts list as map using indexes as keys
sl-to-string(): casts list as string (JS .join())
sl-union(): returns a list of values from given lists minus duplicates
sl-walk(): applies a function to every value of list
If you feel like an explorer, you can have a look at the code here.
Requirements
If you are looking for the last version of SassyLists running on Sass 3.2, install 0.4.9.
If you are looking for the last version of SassyLists running on Sass 3.3, install 2.2.5.
Some functions depend on other functions. If you include functions individually, make sure to check for these dependencies in their respective docs.
Also read
Credits
A lot of thanks to all contributors and to at-import for their support.