Javascript : looping array of arrays. If match found, push to array, if not, create new innerarray

Question

I'm retrieving information from a database. The data looks like this (I've simplified it):

    var example = [
    {'start': 1966, 'end': 1970},
    {'start': 1969, 'end': 1971},
    {'start': 1972, 'end': 1980},
    {'start': 1974, 'end': 1985},
    {'start': 1975, 'end': 1979},
    {'start': 1986, 'end': 1990},
    {'start': 1991, 'end': 1995}
          ];

What I want to do is sort this dynamically into a new, empty array newArr . When the sorting is done newArr should look like

var newArr = [
    [
        {'start': 1966, 'end': 1970},
        {'start': 1972, 'end': 1980},
        {'start': 1986, 'end': 1990},
        {'start': 1991, 'end': 1995}
    ],
    [
        {'start': 1969, 'end': 1971},
        {'start': 1974, 'end': 1985}
    ],      
    [
        {'start': 1975, 'end': 1979}
    ]];

I'm new with javascript. The reason I've chosen for this combination of arrays and objects is because I'm using JSON data in which the order of objects is important

What I want to do and what I tried

I'm trying to group the objects on the different keys of the main array (newArr[0], newArr[1] etc . I want to iterate through example and put objects on a certain key. if in the iteration of example the property end is lower than what at that moment is on newArr, there is an overlap and a new array should be made. Else it should be pushed in to the main array key where where there is no overlap. I've tried doing this with the the following three functions

    var newArr = [];

    function _overlap(){
    // place first object
    var addFirst = [example[0]];
    newArr.push(addFirst);

    // place others, therefore start with i = 1;
    for (var i = 1 ; i < example.length ; i++){
        _checkOverlap(example[i]);  
    }   
}   
_overlap();

    function _checkOverlap(input){
    // traverse the main array newArr, example[i] is passed as argument input
    loopJ:{
        for (var j = 0; j < newArr.length; j++){
            // compare value of input.start (so example[i]) with last key of inner array
            var innerArrayLength = newArr[j].length; // I need this to get the last key: length -1
            if (input.start > newArr[j][innerArrayLength-1].end ){
                newArr[j].push(input);
                console.log(newArr);
                break loopJ;                    
            } else {
                _createNewArr(input);
                break loopJ;
            }
        }           
    }
}

    function _createNewArr(input){
    var toBeAdded = [];
    toBeAdded.push(input);
    newArr.push(toBeAdded);
}

This code does exactly what I want on the first key newArr0 , but never pushes into the other keys. Should I use a recursion in this case? I've tried so many things, but the amount of browsers crashes due to infinite loops is driving me crazy.

Answer 1

If I understand it correctly, for each entry of example you must search the first group in newArr where the entry can be added. If you find that group, add the entry and iterate the next entry. If you don't find that group, just create a new group at the end.

var newArr = [];
outerloop:
for(var entry of example) {
  for(var group of newArr)
    if(group[group.length-1].end < entry.start) {
      group.push(entry);
      continue outerloop;
    }
  newArr.push([entry]);
}

Answer 2

why don't you use a comparator function inside arr.sort

 var example = [
{'start': 1966, 'end': 1970},
{'start': 1969, 'end': 1971},
{'start': 1972, 'end': 1980},
{'start': 1974, 'end': 1985},
{'start': 1975, 'end': 1979},
{'start': 1986, 'end': 1990},
{'start': 1991, 'end': 1995}
      ];

//sorting using comparator function
example.sort(function(a,b){return a.start-b.start}) //will sort on start date