JSON_OBJECT
creates JSON Objects:
SELECT JSON_OBJECT('key1',col1 , 'key2',col2 , 'key3','col3') as myobj;
JSON_ARRAY
creates JSON Array as well:
SELECT JSON_ARRAY(col1,col2,'col3') as myarray;
Note: myobj.key3 and myarray[2] are "col3" as fixed string.
Also mixed JSON data:
SELECT JSON_OBJECT("opening","Sicilian", "variations",JSON_ARRAY("pelikan","dragon","najdorf") ) as mymixed ;