ct | concept tool for writing ruby scripts

The little lighter colored "ct" prompt is just a visual aid and it does not always show up. When you provide a raw value as an argument, it will show the prompt (like this, 1, or "foo"). When you provide a variable for the argument like ctx, foo, etc, it does not show up. This goes for all functions that take arguments.

The moral of the story is, it is not important and can be ignored.

try this

This can be done using slicing:

Is this a solution?

Fiddle: http://sqlfiddle.com/#!18/12e9a0/9

You can loop over the row array, replacing empty values with No data.

Browser caching is determined by the caching headers (namely Cache-Control or Expires) in the response from the origin server. But the response you listed doesn't have such a header, so it's up to the browser to determine how long the resource is considered fresh.

If you want the browser to use a particular cache policy you should add a Cache-Control header to the response.

your problem is the forward slashes in the query-parameter string. If you can remove those (str replace) you can use JS's URLSearchParams.

see: https://www.sitepoint.com/get-url-parameters-with-javascript/

Does the library auto-assign the slave number, or we have to define it?

With MinimalModbus you pass the slave ID through in the minimalmodbus.Instrument('/dev/ttyUSB0', 1) call (the 1 is the Slave ID). How you set the slave ID on the device itself varies (this is not covered by the Modbus over serial line spec; could be a configuration program, DIP switches, based on the serial number etc. Other libraries may take different approaches (for example defaulting to Slave ID 1).

From the datasheet, is it the register number is the address?

The header in the spec tables says "No(Address)" so "10001(0000)" means register 1, address 0 (these refer to the same thing; I recommend reading the "Modbus: When 40001 Really Means 1, or 0 Really Means 1" section in this article which explains some of the issues around addressing).

And how many decimals do I expect if there's two data sequence as a response?

Not quite sure what you mean by "two data sequence". The Modbus spec only details the sending of bits (coils) and 16 bit values (input/holding registers). From a quick look at your spec it looks like this device just uses a single registers; for instance "OUT1 Output time" has "unit: ×10㎳" so take whatever is in the register and divide by 10 to get ms.

Is the CRC16 check already included within the library as i shouldn't code it?

Any decent Modbus library will look after the protocol details (such as CRC) for you (so no you don't need to code this; MinimalModbus will calculate it for you)

The issue is that document.querySelectorAll() returns an array of all the dropdown element in your code, and document.querySelector() returns the first one he founds, but not necessary the one inside the element that fired the event.

If you want to add the active class to the dropdown element contained within the selector element that was clicked, you can call querySelector() from the event current target rather than from document :