Javascript: Merge 2 arrays of objects into a new one, based on object properties-CodePudding

I have 2 arrays of JSON objects in javascript from which I would like to create a new array where I map on the property "Word_No" They look like this:

wordInfo (length 4000):

    [
    {
        "Word_No": "0",
        "Alarm_Bit": "0",
        "Alarm_No": "1",
        "Alarm_Description": "Alarm text 1"
    },
    {
        "Word_No": "0",
        "Alarm_Bit": "1",
        "Alarm_No": "2",
        "Alarm_Description": "Alarm text 2"
    },
    {
        "Word_No": "0",
        "Alarm_Bit": "2",
        "Alarm_No": "3",
        "Alarm_Description": "Alarm text 3"
    }
]

and wordTags (length 250):

    [
    {
        "Word_No": "0",
        "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm0_15"
    },
    {
        "Word_No": "1",
        "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm16_31"
    },
    {
        "Word_No": "2",
        "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm32_47"
    }
]

What I need to become is a new array: Alarmlist (length 4000):

    [
    {
        "OPC Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm0_15",
        "Alarm_Bit": "0",
        "Alarm_No": "1",
        "Alarm_Description": "Alarm text 1"
    },
    {
        "OPC Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm0_15",
        "Alarm_Bit": "1",
        "Alarm_No": "2",
        "Alarm_Description": "Alarm text 2"
    },
    {
        "OPC Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm0_15",
        "Alarm_Bit": "2",
        "Alarm_No": "3",
        "Alarm_Description": "Alarm text 3"
    }
]

When I try to build this function using 2 for loops and mapping on the the Word_No property, it crashes.

    for (i = 0; i < wordInfo.length;   i){  //Outer loop  
    for (j = 0; j < wordTags.length;   j){  //Inner loop
        msg.Info_Word_No = wordInfo[i].Word_No //Woordnr
        msg.Tag_Word_No = wordTags[j].Word_No //Woordnr
        node.send(msg);
    } 
}

When I limit i and j to for example 10, the function executes and shows the word numbers in the debug window.

My idea was to map everything like this:

if(wordInfo[i].Word_No == wordTags[i].Word_No){
            var alarmTagInfo;
            alarmTagInfo.Alarm_No=wordInfo[i].Alarm_No;
            alarmTagInfo.OPC_Tag = wordTags[i].OPC_Tag;
            alarmTagInfo.Alarm_Bit = wordInfo[i].Alarm_Bit;
            msg.payload = alarmTagInfo;
            alarmlist.push(alarmTagInfo);
        }

But since the arrays are too big, the Node Red application just crashes. I'm not sure what would be the efficient way to handle this?

CodePudding user response：

I'd suggest first creating a lookup object for OPC_Tag using Array.reduce() on wordTags - this will improve performance and avoid doing a .find() for each iteration of the loop on wordInfo.

We'd then use Array.map() on wordInfo to create the final result:

let wordInfo = [ { "Word_No": "0", "Alarm_Bit": "0", "Alarm_No": "1", "Alarm_Description": "Alarm text 1" }, { "Word_No": "0", "Alarm_Bit": "1", "Alarm_No": "2", "Alarm_Description": "Alarm text 2" }, { "Word_No": "0", "Alarm_Bit": "2", "Alarm_No": "3", "Alarm_Description": "Alarm text 3" } ]
let wordTags = [ { "Word_No": "0", "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm0_15" }, { "Word_No": "1", "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm16_31" }, { "Word_No": "2", "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm32_47" } ] 

// Create a lookup, mapping Word_No to OPC_Tag
let wordTagsLookup = wordTags.reduce((acc, { Word_No, OPC_Tag }) => { 
    acc[Word_No] = OPC_Tag;
    return acc;
}, {})

let result = wordInfo.map(({ Word_No, Alarm_Bit, Alarm_No, Alarm_Description}) => { 
    return { Alarm_Bit, Alarm_No, Alarm_Description, OPC_Tag: wordTagsLookup[Word_No] };
})

console.log('Result:', result)

.as-console-wrapper { max-height: 100% !important; }

CodePudding user response：

I would suggest to create a Map for the second array, keyed by Word_No. Then map that array to objects where the translation is made with that Map. With object destructuring this can become quite elegant:

// Sample input data
const wordInfo = [{"Word_No": "0","Alarm_Bit": "0","Alarm_No": "1","Alarm_Description": "Alarm text 1"},{"Word_No": "0","Alarm_Bit": "1","Alarm_No": "2","Alarm_Description": "Alarm text 2"},{"Word_No": "0","Alarm_Bit": "2","Alarm_No": "3","Alarm_Description": "Alarm text 3"}];
const wordTags = [{"Word_No": "0","OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm0_15"},{"Word_No": "1","OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm16_31"},{"Word_No": "2","OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm32_47"}];

// Create map keyed by Word_No:
const map = new Map(wordTags.map(({Word_No, OPC_Tag}) => ([Word_No, OPC_Tag])));
// Translate the source data to the target data
const alarmList = wordInfo .map(({Word_No, ...rest}) => 
    ({OPC_Tag: map.get(Word_No), ...rest})
); 
console.log(alarmList);

CodePudding user response：

for me you can make like this, just using .map() and .filter() method :

const wordInfo = [
  {
      "Word_No": "0",
      "Alarm_Bit": "0",
      "Alarm_No": "1",
      "Alarm_Description": "Alarm text 1"
  },
  {
      "Word_No": "0",
      "Alarm_Bit": "1",
      "Alarm_No": "2",
      "Alarm_Description": "Alarm text 2"
  },
  {
      "Word_No": "0",
      "Alarm_Bit": "2",
      "Alarm_No": "3",
      "Alarm_Description": "Alarm text 3"
  },
];

const wordTags = [
    {
        "Word_No": "0",
        "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm0_15"
    },
    {
        "Word_No": "1",
        "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm16_31"
    },
    {
        "Word_No": "2",
        "OPC_Tag": "HH.Application.TmpHmi_Var.TmpHmiC7.Alarm32_47"
    }
];

const data = wordInfo.map((wordInfoItem) => {
  const wordTag = wordTags
    .filter((wordTagItem) => (wordInfoItem["Word_No"] === wordTagItem["Word_No"]))[0];
  
  const newArray = {
    ...wordTag,
    ...wordInfoItem,
  };

  delete newArray['Word_No'];
  return newArray;
});

console.log(data);