Explanation of code help

General
1

@cymplecy posted this code back in January

if (msg.payload == 1) {
    context.set("previousState",!context.get("previousState"))
    msg.payload = 1 * context.get("previousState");
    return msg;
}

I have used this a number of times now and spent the better part of a day googling as to how it worked. I figure if I'm going to use a lot I should understand it. Unfortunately, my google searches all point back to the forum so I am left with no explanation. If someone could please tell me what is happening I would appreciate it.

2

So what happens is the following, if msg.payload == 1.

in the first line:

 context.set("previousState",!context.get("previousState"))

First you get previousState variable from the node context. The content of the is negated by ! - so you have instead of true, false or vice versa. So it acts like a toggle switch. The opposite value is then immediately stored again in the node-context.

The next line:

msg.payload = 1 * context.get("previousState");

As boolean true evaluates to 1 and false to 0 the result is 0 or 1.

To be honest I think the code is in my opinion a little bit laborious.

In my opinion it would be sufficient to use only booleans.

3

Thanks for the help

4

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