Hello.
I am starting with nodeRed.
I am looking for how it can be extracted from a part of a chain,
I expose the message that is received. "C, *, 1234, Z". I want to get the value '1234'.
How should I do it in a function?
Where can I find documentation for working with strings in NODERED?
Thanks and regards.
Why are all of you want to extract somehting with a function node - writing code. Node Red has its strength by using nodes:
[{"id":"7f8eb7fe4b3bf817","type":"inject","z":"cb05e14b.326a9","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"C, *, 1234, Z","payloadType":"str","x":690,"y":580,"wires":[["e7bbf036233cfeed"]]},{"id":"e7bbf036233cfeed","type":"split","z":"cb05e14b.326a9","name":"","splt":",","spltType":"str","arraySplt":1,"arraySpltType":"len","stream":false,"addname":"","x":870,"y":580,"wires":[["1bc94331a3c6cc17"]]},{"id":"93be156fa87a1d48","type":"debug","z":"cb05e14b.326a9","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":1190,"y":580,"wires":[]},{"id":"1bc94331a3c6cc17","type":"switch","z":"cb05e14b.326a9","name":"","property":"parts.index","propertyType":"msg","rules":[{"t":"eq","v":"2","vt":"num"}],"checkall":"true","repair":false,"outputs":1,"x":1020,"y":580,"wires":[["93be156fa87a1d48"]]}]
Because it simpler and allows to trim or convert to a number etc if needed and It is often quicker than sending 4 messages when one will do.
@Manu110 here ar examples of using Javascript and JSONata for the OP
[{"id":"d3712560.b7de8","type":"inject","z":"c791cbc0.84f648","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"C, *, 1234, Z","payloadType":"str","x":160,"y":1160,"wires":[["65da86a0.e11e08"]]},{"id":"65da86a0.e11e08","type":"function","z":"c791cbc0.84f648","name":"","func":"msg.payload = msg.payload.split(\",\")[2].trim()\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":380,"y":1160,"wires":[["98730897.18ec28"]]},{"id":"98730897.18ec28","type":"debug","z":"c791cbc0.84f648","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":660,"y":1160,"wires":[]},{"id":"7f8eb7fe4b3bf817","type":"inject","z":"c791cbc0.84f648","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"C, *, 1234, Z","payloadType":"str","x":160,"y":1060,"wires":[["cd5bff6.e8a8d"]]},{"id":"cd5bff6.e8a8d","type":"change","z":"c791cbc0.84f648","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"$trim($split($$.payload,\",\")[2])","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":410,"y":1060,"wires":[["93be156fa87a1d48"]]},{"id":"93be156fa87a1d48","type":"debug","z":"c791cbc0.84f648","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":660,"y":1060,"wires":[]}]
Ok then we can code all our flows in one function node and then only in-Nodes and out-Nodes messages will be sent. 
If you don't want to use function and code that's fine. P.s. Your flow results in 4 times the number of messages sent and still you have not parsed the "1234" correctly.
@cymplecy I like your thought. You could also target the specific string as below
