T-SQL to return contents of a table as a JSON object

pGetJSONFromTable.sql

//Gets all records in a SQL table and returns it as a single-dimension JSON object.
//If the parameter @VarName is passed, the returned output assignes the object to that variable.

CREATE PROCEDURE [dbo].[pGetJSONFromTable] @ObjectName VARCHAR(255), @VarName VARCHAR(255) = NULL, @registries_per_request smallint = null

AS

BEGIN
    
    IF OBJECT_ID(@ObjectName) IS NULL
        BEGIN
            SELECT Json = '';
            RETURN
        END;
    

    DECLARE @Top NVARCHAR(20) = CASE WHEN @registries_per_request IS NOT NULL 
                                    THEN 'TOP (' + CAST(@registries_per_request AS NVARCHAR) + ') ' 
                                    ELSE '' 
                                END;

    DECLARE @SQL NVARCHAR(MAX) = N'SELECT ' + @Top + '* INTO ##T ' + 
                                'FROM ' + @ObjectName + '';

    EXECUTE SP_EXECUTESQL @SQL;

    DECLARE @X NVARCHAR(max) = N'[' + (SELECT * FROM ##T FOR XML PATH('')) + ']';
	
    SET	@X = N'' + REPLACE(@X, CHAR(10), '\n')
	SET	@X = N'' + REPLACE(@X, CHAR(13), '')
	SET	@X = N'' + REPLACE(@X, '"', '"')
	SET	@X = N'' + REPLACE(@X, '''', ''')
	

    SELECT  @X = REPLACE(@X, '<' + Name + '>', 
                    CASE WHEN ROW_NUMBER() OVER(ORDER BY Column_ID) = 1 THEN '{"'
                         ELSE '"' END + Name + '":"'),
            @X = REPLACE(@X, '</' + Name + '>', '",'),
            @X = REPLACE(@X, ',{', '}, ' + CHAR(13) + CHAR(10) + '{'), 
            @X = REPLACE(@X, ',]', '}]')
            
    FROM    sys.columns
    WHERE   [Object_ID] = OBJECT_ID(@ObjectName)
    ORDER BY Column_ID;

    DROP TABLE ##T;

    SELECT  Json = ISNULL('var ' + @VarName + ' = ', N'') + @X, 
            len(@x) AS Length;

END

GO