Here is an example of a trivially obfuscated HTML code where browser based tools are used to reverse that obfuscation.
For some this can appear startling, but it is perfectly normal as the web browser must ‘see’ this code for it to render the page and allow the user to interact with it. What is protected on the server is still protected there, but the browser is a completely different problem and this code ‘in the clear’ makes protecting client-side a challenge.
At this point you might just take that as an acceptable risk for your project, though of course, you can still go some way to reduce that risk. There are a number of techniques or design approaches that can be taken to minimise the exposure of what makes your product different from all the others, while both still allowing the user to effectively operate it as well as provide some, but not perfect, protection against the curious.
The first and easiest design consideration is to move as much of the logic you want to protect to the server side where you can protect it via the ionCube Encoder. Obviously not everything can go there and there will always have to be something client-side.