Editing Module:CountryData/doc (section)

=== getalias ===
If used from wikicode, this function returns the value of a single field in a data template. The first parameter is the country or other entity whose data to return; the second is the name of the field. For example, <code>{{((}}#invoke:CountryData|getalias|France|flag alias{{))}}</code> &rarr; {{#invoke:CountryData|getalias|France|flag alias}}. The other parameters are {{para|variant}} to return a variant parameter value, with fallback to the main field value if the variant does not exist, and {{para|def}} for the fallback output if the wanted data template or field does not exist, the default for which is a literal "nil".

Note: This is likely not quicker than wikicode-only alternatives such as {{tl|getalias}} and {{tl|getalias2}}, because it transcludes the data template from Lua and converts it to a Lua table using the above function, picks the wanted parameter name, and returns it to wikicode, whereas other templates perform two simple non-Lua transclusions to get, in most cases, the same result. The Lua version does have the advantage that using it with a non-existing country data template returns "nil" (or the value of {{para|def}}) rather than a redlink to the data template. See a comparison of the four at [[User:SiBr4/Flagg tests#Lua-based getalias|User:SiBr<sub>4</sub>/Flagg tests#Lua-based getalias]].