Extra Map Functions in Sass

Originally published at: http://www.sitepoint.com/extra-map-functions-sass/

Sass maps are awesome. They make a lot of things that were previously impossible, well, possible. For instance, they have a smart way to define dynamic variables. They are also the perfect container for a complex configuration, for a framework or a grid system.

Fortunately for us, Sass provides a handful of functions to manipulate maps. Yet, if you keep working with Sass you might come up with an edge case that is not being covered by the built-in API.

Perhaps you’ll need a way to get a key that is being nested within several maps? What if you want to update this key? Or extend nested maps like $.extend from jQuery? A few problems here and there that can be easily fixed with the functions we’ll inspect today.

Map Deep Get

When you need to access a key that belongs to a map which happens to be nested within another map (or several), you cannot rely on map-get anymore. At least, not as it currently is.

/// Fetch nested keys
/// @param {Map} $map - Map
/// @param {Arglist} $keys - Keys to fetch
/// @return {*}
@function map-deep-get($map, $keys...) {
  @each $key in $keys {
    $map: map-get($map, $key);

  @return $map;


$grid-configuration: (
  'columns': 12,
  'layouts': (
    'small': 800px,
    'medium': 1000px,
    'large': 1200px,

// Without `map-deep-get`
$medium: map-get(map-get($grid-configuration, 'layouts'), 'medium');

// With `map-deep-get`
$medium: map-deep-get($grid-configuration, 'layouts', 'medium');

Map Deep Set

As you can see, building a function to get a key from within nested maps is not overly difficult to write. On the other hand, a function to set a value at the end of a key chain is not as easy to build… Because of the complexity, we will not get too deep into the code for this one.

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Some nice functions there. Deep get is probably the most useful.
I don’t really see the point of map-zip… actually I just realised that if your using loops to generate your keys and values then that could come in handy.

I really don’t like arg lists though. I see the commas in functions as important separaters that define different functionality applied to each value in between those brackets.

It makes the functions more difficult to understand when you have this sort of layout:

@function function_name($map, $key, $values…){ };

function_name($map, key, val, val, val, val);

I think this makes more sense:

@function function_name($map, $key, $values){ };

function_name($map, key, val val val val);

The commas clearly define where the difference is in functionality on the second example. In the first example, it can be difficult to tell when the list of values actually starts.

Also there is the benefit of the list not having to be the last thing in the function brackets, so you can put the list earlier in the chain and set defaults for the variables after it.

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