What is the best to debug custom js in a form. A form is referencing js fil

I put an additional text field and a checkbox in the form. In the onclick event of the checkbox I put code to evaluate the text in the text field as javascript using the "eval" function. This way it is quite easy to check and debug JS directly in the form. As soon as it works the way I want, I copy the code and use it in the forms editor.

I put an additional text field and a checkbox in the form. In the onclick event of the checkbox I put code to evaluate the text in the text field as javascript using the "eval" function. This way it is quite easy to check and debug JS directly in the form. As soon as it works the way I want, I copy the code and use it in the forms editor.