Regex match in function node?

General
1

The switch node allows me to match the following regex in a string:
^\#\?[1-3][0-6]$

I'd like to do this in a function node. I tried:

if (msg.payload.search("^\#\?[1-3][0-6]$") > -1) {
    // blah
    return msg;
}

But it doesn't work, i.e. the match is clearly not found as msg is not returned.

What's wrong here?

(Why do I want to do this in a function node? I have a few different matches I want to perform, with different code blocks for each one, and I want to see it clearly on one page which match applies to which code block without having to switch back and forth between the switch node and the function node)

2

hello .. you need slashes wrapping the regex

[{"id":"03084b6a8123d65d","type":"function","z":"5847b7aa62131d37","name":"","func":"\nmsg.payload = msg.payload.match(/^\\#\\?[1-3][0-6]$/)\n\nif (msg.payload) {\n    node.warn(msg.payload[0]);   // first match\n    return msg;\n}\n\n\n\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":560,"y":1560,"wires":[["10663b0e50f5fd9e"]]},{"id":"eaafbd92ddb9c638","type":"inject","z":"5847b7aa62131d37","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"#?25","payloadType":"str","x":390,"y":1480,"wires":[["03084b6a8123d65d"]]},{"id":"10663b0e50f5fd9e","type":"debug","z":"5847b7aa62131d37","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":770,"y":1560,"wires":[]},{"id":"d8b0fe4ae2d41355","type":"inject","z":"5847b7aa62131d37","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"#25","payloadType":"str","x":390,"y":1540,"wires":[["03084b6a8123d65d"]]},{"id":"100f24e3319532a9","type":"inject","z":"5847b7aa62131d37","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"#?55","payloadType":"str","x":390,"y":1600,"wires":[["03084b6a8123d65d"]]},{"id":"257a5fb774798e73","type":"inject","z":"5847b7aa62131d37","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"#?36","payloadType":"str","x":390,"y":1660,"wires":[["03084b6a8123d65d"]]}]
3

Best use /pattern/ in javascript then you can use modifiers etc

Your regex starts with ^, which means start of string. $ at end means end of string.
So unless your string starts with # and ends with 0-6, it will always return -1.
Try removing the $ and ^.

4

Thanks - that solves it!

5

Yep, the regex was correct (message always starts with # and ends with 0-6 in this case...) - I just didn't use the forward slashes correctly! Thanks

6

The use of search() threw me off as i thought you were looking for an index of the first match. Would it not be better to use test() as it returns true or false?

7

I didn't know about that, looks like that may technically be better, although for this purpose it does pretty much the same thing I think?

8 
if (msg.payload.test(/^\#\?[1-3][0-6]$/) ) {
    // blah
    return msg;
}

But cleaner in the code.

1 Like
9

i think for test() the regex has to first

if ( /^\#\?[1-3][0-6]$/.test(msg.payload) ) {
   
 return msg;
}
10

I have another question now, similar topic!

I have incoming message like this:

#>1101102582759203918490

It consists of:
# then > then [1-3] then [1-6] then any 20 digits - in that exact format.

I have regex which works in an online regex tester:
^\#\>[1-3][1-6]\d{20}$

But when I do this in Node-RED function it doesn't work:

if (msg.payload.search(/^\#\>[1-3][1-6]\d{20}$/) != -1) {
    // blah
}

This is strange, because my first two regex matches worked in the same way. This works ok for the message #?15:

if (msg.payload.search(/^\#\?[1-3][0-6]$/) != -1) {
    // blah
}
11 
[{"id":"03084b6a8123d65d","type":"function","z":"5847b7aa62131d37","name":"","func":"\nif (/^\\#\\>[1-3][1-6]\\d{20}$/.test(msg.payload)) {\n    \n    return msg;\n}\n\n\n\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":580,"y":1620,"wires":[["10663b0e50f5fd9e"]]},{"id":"10663b0e50f5fd9e","type":"debug","z":"5847b7aa62131d37","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":750,"y":1620,"wires":[]},{"id":"e577b0b8725cf17c","type":"inject","z":"5847b7aa62131d37","name":"#>1101102582759203918490","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"#>1101102582759203918490","payloadType":"str","x":340,"y":1600,"wires":[["03084b6a8123d65d"]]},{"id":"5bd01e16d7f98336","type":"inject","z":"5847b7aa62131d37","name":"#>11011025827","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"#>11011025827","payloadType":"str","x":360,"y":1660,"wires":[["03084b6a8123d65d"]]}]
12

Ahh - found the problem. My device was returning an additional space at the end :slight_smile: Thanks

1 Like
13

i was wondering because i tested with search() syntax also and it was working for me :wink:

14

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