Assertion: function's argument | /r/HasProperty | string
Facets:
value: for objects
type: TRANSITIVE-OBJECT
value: in the first function call
type: TEMPORAL
Source sentences:
text: The only formal argument for the function is a string that specifies the characters that separate the items to concatenate.
text: In the first function call, the argument is a string.
text: The first argument is the current index, which is either a number (for arrays) or string (for objects).