OnSubmit Client script to set value of assignment group

[Deepika Mishra]

I am trying to set value of assignment group using client script on onSubmit functionality, but the below code is not working. Please help :

[Brandon Barret1]

I would use an onChange script for this, is there a reason you are using onSubmit? 

[Deepika Mishra]

yes it has to execute onsubmit

[Elijah Aromola]

Have you checked to make sure your condition is actually true? Is the value of the field tax? 
can you add an alert statement to show "authorityValue"?

[Deepika Mishra]

I have added an alert Inside tax and am able to see that on clicking submit button.