Question 110174 in Json Question posted in
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Javascript: How to reduce json when consecutive key is the same?

I have a json where I need to reduce the items when they are of a type (isSender).
I need to reduce them when they are occurring consecutively.
The data can change.

The data looks like this:

 "messages": [
    { "content": ["Foo"], "isSender": true },
    { "content": ["Bar"], "isSender": true },
    { "content": ["Lorem"], "isSender": true },
    { "content": ["Ipsum"], "isSender": true },
    { "content": ["Dolor"], "isSender": false },
    { "content": ["Sit Amet"], "isSender": false },
    { "content": ["No"], "isSender": true }
  ]

I need the content to be an array of messages when the consecutive isSender key is the same. The output should look like this:

  "messages": [
    {
      "content": ["Foo", "Bar", "Lorem", "Ipsum"],
      "isSender": true
    },
    { "content": ["Dolor", "Sit amet"], "isSender": false },
    { "content": ["No"], "isSender": true }
  ]

So far I have tried looping through the message array and checking if next messages have the same isSender key. However this does not work for more than 2 messages.

let deleteIndex = [];
 for(let i = 0  ; i < messages.length - 1; i++) {
        const currMs = messages[i];
        const nextMs = messages[i + 1];
        if (nextMs.isSender == currMs.isSender) {
            currMs.content.push(nextMs)
            deleteIndex.push(i + 1) // saving index to be deleted once for loop is done
        }
    }

Can someone give me a clue on how to work around this?

Thanks in advance.

Tags:

2

Answers


  1. 0

    you can try this

    var res = {
  messages: [
    { content: [], isSender: true },
    { content: [], isSender: false },
    { content: [], isSender: false }
  ]
};

messages.messages.forEach((item) => {
  if (item.content[0] == "No")  {
res.messages[2].content = ["No"];
res.messages[2].isSender = item.isSender;
  }
  else {
    if (item.isSender)
       res.messages[0].content.push(...item.content);
    else res.messages[1].content.push(...item.content);
  }
});

console.log(JSON.stringify(res, null, 4));

    json output

    {
  "messages": [
    {
      "content": [
        "Foo",
        "Bar",
        "Lorem",
        "Ipsum"
      ],
      "isSender": true
    },
    {
      "content": [
        "Dolor",
        "Sit Amet"
      ],
      "isSender": false
    },
    {
      "content": [
        "No"
      ],
      "isSender": true
    }
  ]
}
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  2. 0

    Use reduce(), on each iteration, we check if the last element in the result array has the same isSender value as the current object we’re dealing with.

    if (p.length && p.at(-1).isSender === c.isSender) {

    So, if we already have something in the final array (p.length) AND the last isSender (p.at(-1).isSender) has the same value as the current isSender (c.isSender), append to that content list

    Otherwise, add the entry, which is just the current object itself (return [ ...p, c ])

    const data =  [
    { "content": ["Foo"], "isSender": true },
    { "content": ["Bar"], "isSender": true },
    { "content": ["Lorem"], "isSender": true },
    { "content": ["Ipsum"], "isSender": true },
    { "content": ["Dolor"], "isSender": false },
    { "content": ["Sit Amet"], "isSender": false },
    { "content": ["No"], "isSender": true }
  ];
  
const res = data.reduce((p, c) => {
    if (p.length && p.at(-1).isSender === c.isSender) {
        p.at(-1).content.push(...c.content);
        return p;
    }
    return [ ...p, c ];
}, [])

console.log(res);

    Should you not like the push way, we can use Object.assign to alter the index itself:

    let i = p.length - 1;
return Object.assign([...p], { [i]: { ...p[i], content: [ ...p[i].content, ...c.content ]}});

    const data =  [
    { "content": ["Foo"], "isSender": true },
    { "content": ["Bar"], "isSender": true },
    { "content": ["Lorem"], "isSender": true },
    { "content": ["Ipsum"], "isSender": true },
    { "content": ["Dolor"], "isSender": false },
    { "content": ["Sit Amet"], "isSender": false },
    { "content": ["No"], "isSender": true }
  ];
  
const res = data.reduce((p, c) => {
    if (p.length && p.at(-1).isSender === c.isSender) {
        let i = p.length - 1;
        return Object.assign([...p], { [i]: { ...p[i], content: [ ...p[i].content, ...c.content ]}});
    }
    return [ ...p, c ];
}, [])

console.log(res);

    Javascript spread on array index to 'push' new item to nested array

    [
  {
    "content": ["Foo", "Bar", "Lorem", "Ipsum"],
    "isSender": true
  },
  {
    "content": ["Dolor", "Sit Amet"],
    "isSender": false
  },
  {
    "content": ["No"],
    "isSender": true
  }
]
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