Hi, yesterday I've became a bit crazy knowing why the code didn't work, in particular I was defining the desidered output node's object message into an if code, the deploy didn't notify an error but the message could't be output, like the code inside the "if" { code } was not executed. It was executed but the "let" command coudn't be written there, it should be outside the "if".
I would suggest to help users, checking this and marking it as an error.
Struggling to understand the situation here Giovanni.
Perhaps you could show us a function code to illustrate the point?
Ok, for example:
let output = {};
if (msg.payload) {output = {works:true};}
return output;
if (msg.payload) {let output = {works:false};} else {let output = {works:false};}
return output;
the second example oesn't return errors, the code is executed but message output is not defined/created
That is perfectly legal javascript, but when you use let inside a {} block then it declares a new variable local to the block. Inside the block the original variable is not accessible. Your code should be
if (msg.payload) {
output = {works:false};
} else {
output = {works:false};
}
return output;
[Edit] it seems a bit odd to have the same code in the if and in the else.
Also, as @jbudd has noted, you need let output before the if
For me this code is not flagged as an error in the editor, but it does give a run-time error
if (msg.payload) {
let output = {works:false};
}
else {
let output = {works:false};
}
return output;
ReferenceError: ReferenceError: output is not defined (line 7, col 1)
(Because of course output only has a value within the two sets of braces where it is declared.)
I suppose one might hope that the code editor was smart enough to check the variable scope, but apparently it's not - unless there is a setting somewhere for this.
It is a bit uncomfortable to have to declare let output or let output = {} somewhere at the top, especially if you come from a language where variables don't need to be declared.
In addition to jbudd message, you can try with:
If you install nrlint from the .node-red folder
npm install nrlint
then the code does generate warnings.
Thank you everyone, now I've understood. Yes it has perfectly sense to declare variables only on particular {scope}, but I dubt it's really useful, anyway that's it.
I didn't now that before, better for me install nrlint to avoid such misunderstandings in future
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