function isArrayIndexString( prop ) {
	return ( isString( prop ) && RE_ARRAY_INDEX.test( prop ) );
}
Tests if an indexing expression is a serialized array index.

@private
@param {(string|symbol)} prop - property name
@returns {boolean} result

@example
var out = isArrayIndexString( 'ArrayIndex<0>' );
// returns true

@example
var out = isArrayIndexString( ':' );
// returns false