SCSS : Checking if a value exists in a multi dimensional list

Question

I'm using Sass (v3.3.0.alpha.392), and I have a multi-dimensional list that looks somewhat like this,

$list: (
config: (
    foo: (
        a: 1,
        b: 2,
    ),
    bar: (
        a: 3,
        b: 4,
    ),
));

I have a @mixin that takes an argument, and will output based on which argument is passed if it exists in the config $list. Something like this,

@mixin foo($arg) {
    @if $arg exists in $list == true { // is 'foo' or 'bar'
        // Do something
    } @else {
        @warn "failed.";
    }
}

Usage,

.test {
    @include foo(bar); // should return true and run code block
    @include foo(data); // should return false and @warn
}

But, I cannot find the correct function to check if $arg exists in $list. I have tried small functions that check the index,

@function exists($n) {
    @return (false == index($list, config $n));
}

But, this don't seem to work (I might just be using it incorrectly). I basically need this to switch between different operations based on if the arg is contained in the $list.

Also, might be a double question, but is there also any way to check if the $arg is an integer or string? Would also be very helpful.

Thanks!

Answer 1

Your $list is actually a map:

type-of($list) == map

And if I understand correctly, you are interested in matching your keys to a value (e.g. bar).
There is a function called map-has-key($map, $key) that returns true if it finds the matching key, but in a multidimensional map it only matches keys in the topmost level. However, you can write a simple wrapper function that recursively apply map-has-key through all the levels of your map until it finds a match. The wrapper function could be something like this:

@function rmhk($m, $a){
    @if map-has-key($m, $a) { @return true; };
    @each $key,$e in $m {
      @if (type-of($e) == map) and rmhk($e, $a) { @return true; }
    }
  @return false;
}

DEMO

The same way (with a recursive function) you can also match the values in your map in addition to the keys or traverse a list instead of a map (DEMO with value-matching in a multidimensional list).

And, as already pointed out by @Jeremy, you can use type-of() to check for the type of a variable (like string,number,list,map,color), but if for some reason you need to check for something more specific you would need a custom function (for example, this short function for checking if a value is an integer: DEMO).