Javascript array grouping

Question

Hi I'm trying to group my array by merge siblings if it has a same key with the same value

      let array = [
        {el: 1, ready: true},
        {el: 2, ready: false},
        {el: 3, ready: false},
        {el: 4, ready: false},
        {el: 5, ready: true},
        {el: 6, ready: true},
        {el: 7, ready: false},
      ];

want to map like this

      let arrayGroup = [
        [
          {el: 1, ready: true},
        ],
        [
          {el: 2, ready: false},
          {el: 3, ready: false},
          {el: 4, ready: false}
        ],
        [
          {el: 5, ready: true},
          {el: 6, ready: true}
        ],
        [
          {el: 7, ready: false}
        ]
      ];

The posted question does not appear to include any attempt at all to solve the problem. StackOverflow expects you to try to solve your own problem first, as your attempts help us to better understand what you want. Please edit the question to show what you've tried, so as to illustrate a specific problem you're having in a minimal reproducible example. For more information, please see How to Ask and take the tour. — CertainPerformance
– CertainPerformance, Commented Oct 6, 2018 at 8:50

protoproto · Accepted Answer · 2018-10-06 08:47:28Z

You can follow my method:

let array = [
        {el: 1, ready: true},
        {el: 2, ready: false},
        {el: 3, ready: false},
        {el: 4, ready: false},
        {el: 5, ready: true},
        {el: 6, ready: true},
        {el: 7, ready: false},
      ];
/*
      let arrayGroup = [
        [
          {el: 1, ready: true},
        ],
        [
          {el: 2, ready: false},
          {el: 3, ready: false},
          {el: 4, ready: false}
        ],
        [
          {el: 5, ready: true},
          {el: 6, ready: true}
        ],
        [
          {el: 7, ready: false}
        ]
      ];
*/
var arrayGroup = [];
array.forEach((current,index)=>{
  if(index===0){
    arrayGroup.push([{el:current.el, ready:current.ready}]);
  }else{
    //check previous group if same will add to there, or not same, will add to new 
    if(current.ready === array[index-1].ready){
      arrayGroup[arrayGroup.length-1].push({el:current.el, ready:current.ready});
    }else{
      arrayGroup.push([{el:current.el, ready:current.ready}]);
    };
  };
});
console.log(arrayGroup);

Willem van der Veen · Accepted Answer · 2018-10-06 09:01:51Z

0

This should work:

let array = [{
    el: 1,
    ready: true
  },
  {
    el: 2,
    ready: false
  },
  {
    el: 3,
    ready: false
  },
  {
    el: 4,
    ready: false
  },
  {
    el: 5,
    ready: true
  },
  {
    el: 6,
    ready: true
  },
  {
    el: 7,
    ready: false
  },
];

let previousArrValue = array[0].ready;
let newArrayBuilt = [];
let newArr = [];

for (let i = 0; i < array.length; i++) {


  if (array[i].ready !== previousArrValue) {
    newArrayBuilt.push(newArr);
    newArr = [];
  }


  previousArrValue = array[i].ready;
  newArr.push(array[i]);

  if (i + 1 === array.length) {
    newArrayBuilt.push(newArr);
    break;
  }


}

console.log(newArrayBuilt)

answered Oct 6, 2018 at 9:01

Willem van der Veen

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Comments

Marco Luzzara · Accepted Answer · 2018-10-06 09:19:41Z

0

In this situation Array.reduce can be helpful. For each object visited, it is returned the ready property, that becomes the next accumulator.

  let starter = !array[0].ready;
  let new_arr = [];
  let new_index = -1;

  array.reduce((acc, cur, index, arr) => {
    if (acc != arr[index].ready)
    {
        new_arr.push([cur]);
        new_index++;
    }
    else
    {
        new_arr[new_index].push(cur);
    }

    return cur.ready;
  }, starter);

new_arr is the array you need. In this case an initial value (starter) is needed so that the reduce function begins with a creation of a new sub-array.

edited Oct 6, 2018 at 9:19

answered Oct 6, 2018 at 9:14

Marco Luzzara

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Comments

Mohammed Ashfaq · Accepted Answer · 2018-10-07 06:25:03Z

0

let array = [
  {el: 1, ready: true},
  {el: 2, ready: false},
  {el: 3, ready: false},
  {el: 4, ready: false},
  {el: 5, ready: true},
  {el: 6, ready: true},
  {el: 7, ready: false},
];

let currentReadyStatus = array[0].ready;
finalArray = [[]];
currentIndex = 0;

array.forEach((item) => {
  if(item.ready === currentReadyStatus)
     finalArray[currentIndex].push(item);
  else{
    currentReadyStatus = !currentReadyStatus;
    currentIndex += 1;
    finalArray[currentIndex] = [item]
  }
})

console.log(finalArray)

answered Oct 7, 2018 at 6:25

Mohammed Ashfaq

3,4262 gold badges19 silver badges24 bronze badges

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