Why is JavaScript runtime error when running in design mode?

Question

In VS2010 design mode when I press F5 to run the program, I get the following error: 1. JavaScrip runtime error: Unable to set property 'showmessagebox' of undefined or null reference. 2. JavaScrip runtime error: Unable to set property 'evaluationfunction' of undefined or null reference. When this error I have to press Continue will continue to run, how to fix it ? You see my attached photo file. https://imgur.com/50sExkp https://imgur.com/11T0RiN

Dong Lam Trien · Answer

When running with IE, strange files appear while running with other browsers not like Chorom, ... can you know the cause of this error ? https://imgur.com/L2URPQR https://imgur.com/WfeQpRF

Joginder Banger · Answer

if ( typeof my_obj. showmessagebox === "undefined" ){ console.log( 'the property is not available...' ); // print into console } Before the value assign in showmessagebox and evaluationfunction, just check the those property is undefined or null. I have check you can see above in code. If you want make a common function to checking the property undefined or Null. function validateProperty(Property) { var IsUndefined = false ; if ( typeof Property === "undefined" || Property === null ) { IsUndefined = true ; } return IsUndefined; } Thanks Joginder Singh

Dong Lam Trien · Answer

The error occurred when I use IE, other browsers do not have this error

Ashutosh Gupta · Answer

can you share ur code, it is diffcul to say why this error occured.. you can find few knowl issue solution here https://stackoverflow.com/questions/27038560/javascript-runtime-error-unable-to-set-property