code: function value(key) {
      return function(strMap) {
        return Object.prototype.propertyIsEnumerable.call (strMap, key) ?
               Just (strMap[key]) :
               Nothing;
      };
    }
docs: # value :: String -> StrMap a -> Maybe a . . Retrieve the value associated with the given key in the given string map. . . Formally, `value (k) (m)` evaluates to `Just (m[k])` if `k` is an . enumerable own property of `m`; `Nothing` otherwise. . . See also [`prop`](#prop) and [`get`](#get). . . ```javascript . > S.value ('foo') ({foo: 1, bar: 2}) . Just (1) . . > S.value ('bar') ({foo: 1, bar: 2}) . Just (2) . . > S.value ('baz') ({foo: 1, bar: 2}) . Nothing . ```