SQL Server

Prevent JavaScript Infinite Loops

See more JavaScript Examples

Demonstrates how prevent infinite loops or prevent the JavaScript from running for a longer amount of time than allowed. SQL Server

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    -- This is the JavaScript we'll run:

    -- console.log('Starting infinite loop...'); while(true) {};

    DECLARE @sbScript int
    EXEC @hr = sp_OACreate 'Chilkat.StringBuilder', @sbScript OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    EXEC sp_OAMethod @sbScript, 'Append', @success OUT, 'console.log(''Starting infinite loop...''); while(true) {};'

    DECLARE @js int
    EXEC @hr = sp_OACreate 'Chilkat.Js', @js OUT

    -- Set a limit on the amount of time (in seconds) the script is allowed to run.
    -- If the JavaScript takes longer than this amount of time, then Chilkat kills the script without crashing the host program.
    -- The default value of TimeoutSeconds is 0, which indicates no limit.
    -- For this example, set a limit of 2 seconds.
    EXEC sp_OASetProperty @js, 'TimeoutSeconds', 2

    DECLARE @result int
    EXEC @hr = sp_OACreate 'Chilkat.JsonObject', @result OUT

    EXEC sp_OASetProperty @result, 'EmitCompact', 0

    -- Run the script..
    EXEC sp_OAMethod @js, 'Eval', @success OUT, @sbScript, @result
    IF @success = 0
      BEGIN
        -- Examine the result for an exception.
        EXEC sp_OAMethod @result, 'Emit', @sTmp0 OUT
        PRINT @sTmp0

        -- The result contains this:

        -- 	{
        -- 	  "exception": {
        -- 	    "message": "interrupted - JavaScript exceeded the Chilkat.Js.TimeoutSeconds",
        -- 	    "stack": [
        -- 	      {
        -- 	        "func": "<eval>",
        -- 	        "file": "<input>",
        -- 	        "line": 1,
        -- 	        "col": 8
        -- 	      }
        -- 	    ]
        -- 	  }
        -- 	}

        -- Also examine the LastErrorText.
        EXEC sp_OAGetProperty @js, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @sbScript
        EXEC @hr = sp_OADestroy @js
        EXEC @hr = sp_OADestroy @result
        RETURN
      END

    -- We should never get here..

    PRINT 'Succeeded.'
    EXEC sp_OAMethod @result, 'Emit', @sTmp0 OUT
    PRINT @sTmp0

    EXEC @hr = sp_OADestroy @sbScript
    EXEC @hr = sp_OADestroy @js
    EXEC @hr = sp_OADestroy @result


END
GO