# Merge 2 arrays and covert it to string

**URL:** <https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240>\
**Category:** General\
**Created:** [28 October 2019 16:59 UTC](https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240 "2019-10-28T16:59:08Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![zakaria](https://avatars.discourse-cdn.com/v4/letter/z/b5ac83/32.png) [@zakaria](https://discourse.nodered.org/u/zakaria)\
**Post date:** [28 October 2019 16:59 UTC](https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240/1 "2019-10-28T16:59:08Z")

</div>

Hello  
i have a modbus machine respond with (2 arrays) value , msg.payload[0] is the most significant and msg.payload[1] is the Least significant

![Capture2](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/b/bf2f377e06fc52ef45baf81c6dcfc41631a3143a.png)

so i want to merge this two arrays in one and covert it to string (start with 0x...)

like this ![Capture3](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/3/3ed5f49b22f7045546347f9b57c44e2ec62e564f.png)

Thank you for your help !

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<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [28 October 2019 17:15 UTC](https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240/2 "2019-10-28T17:15:20Z")

</div>

Can you copy the input array and paste it here?

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<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [28 October 2019 17:30 UTC](https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240/3 "2019-10-28T17:30:40Z")

</div>

This does what you asked for but not, I think, what you meant:

```auto
[{"id":"12ee2679.01330a","type":"inject","z":"586832c7.9dc7fc","name":"","topic":"","payload":"","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":250,"y":1740,"wires":[["6d4603bd.67f33c"]]},{"id":"6d4603bd.67f33c","type":"function","z":"586832c7.9dc7fc","name":"","func":"msg.payload = {\n input: [17354, 784],\n}\n\nmsg.payload.output = `0x${msg.payload.input[0].toString(16)}${msg.payload.input[1].toString(16)}`\n\n\nreturn msg;","outputs":1,"noerr":0,"x":390,"y":1740,"wires":[["d73f8f6e.e183c"]]},{"id":"d73f8f6e.e183c","type":"debug","z":"586832c7.9dc7fc","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":610,"y":1740,"wires":[]}]

```

The reason I think it is wrong is that the output with the given input is not the expected 32bit output. Though I may be making more assumptions than warranted.

You probably need to use `padStart` with a leading zeros to make each string 4 characters long?

The result as written gives a value of 71,082,768 (0x43CA310), whereas you may want 1,137,312,528‬ (0x43CA0310)?

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<div class="post-metadata">

**Author:** ![zakaria](https://avatars.discourse-cdn.com/v4/letter/z/b5ac83/32.png) [@zakaria](https://discourse.nodered.org/u/zakaria)\
**Post date:** [29 October 2019 08:11 UTC](https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240/4 "2019-10-29T08:11:37Z")

</div>

thank you , that works !

 ![Capture%204](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/b/b2bedcf71d7404ab0de917c69e8c5cfd7fba9c90.png)

with some editing on the node-red function ...

this is the js code : (for the function)

```auto
var highs = msg.payload[0];
var lows = msg.payload[1];
msg.payload = `0x${highs.toString(16)}${lows.toString(16)}`

return msg;

```

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<div class="post-metadata">

**Author:** ![zakaria](https://avatars.discourse-cdn.com/v4/letter/z/b5ac83/32.png) [@zakaria](https://discourse.nodered.org/u/zakaria)\
**Post date:** [29 October 2019 08:57 UTC](https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240/5 "2019-10-29T08:57:05Z")

</div>

> [@TotallyInformation](#):
>
> The result as written gives a value of 71,082,768 (0x43CA310), whereas you may want 1,137,312,528‬ (0x43CA0310)?

yes this is another problem, when the low word has a "0" at the beginning, the function convert it to string without "0" so the result is wrong ...

how can i solve this please ?

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<div class="post-metadata">

**Author:** ![zakaria](https://avatars.discourse-cdn.com/v4/letter/z/b5ac83/32.png) [@zakaria](https://discourse.nodered.org/u/zakaria)\
**Post date:** [29 October 2019 11:03 UTC](https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240/6 "2019-10-29T11:03:42Z")

</div>

WOW !

i think i solved this problem

```auto
var hhigh = msg.payload.buffer[0];
var lhigh = msg.payload.buffer[1];
var hlow = msg.payload.buffer[2];
var llow = msg.payload.buffer[3];

    if (hhigh < 0x0F) {var hhighs = `0${hhigh.toString(16)}`;}
    else { hhighs = `${hhigh.toString(16)}`;}

    if (lhigh < 0x0F) {var lhighs = `0${lhigh.toString(16)}`;}
    else {lhighs = `${lhigh.toString(16)}`;}

    if (hlow < 0x0F) {var hlows = `0${hlow.toString(16)}`;}
    else {hlows = `${hlow.toString(16)}`;}

    if (llow < 0x0F) {var llows = `0${llow.toString(16)}`;}
    else {llows = `${llow.toString(16)}`;}

msg.payload = `0x${hhighs}${lhighs}${hlows}${llows}`
return msg;

```

enjoy !

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<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [29 October 2019 12:00 UTC](https://discourse.nodered.org/t/merge-2-arrays-and-covert-it-to-string/17240/7 "2019-10-29T12:00:54Z")

</div>

There is a much simpler method and I gave you a clue. It is easiest to convert once you have each number as a string. Given that you only need to prefix with zero's. Assuming you are using at least node.js v8+ you have access to ES6 and therefore can use the string function `mystring.padStart(4,'0')`.