array in for loop merge with second for loop array javascript

Question

I have a problem merging 2 arrays in an for loop see code:

function count_days(tijden,datums ){

        var length = tijden.length;
        element = null;
        var similarities =0;
        var backup = [];
        var dateArray =[];

        for (var i = 0; i <length; i++) {
                element = tijden[i];
                tijden[i] = element;


            dateArray = getDates(new Date(tijden[i]['begin']), new Date(tijden[i]['eind']));


         }

The problem is that when the code is running i get one array for each loop. I need to get one array with the data from all loops. I tryde concat but didnt get this to work

Answer 1

It should be...

dateArray.push(
  getDates(new Date(tijden[i]['begin']), new Date(tijden[i]['eind']))
);

... or, if getDates method returns an array and you want dateArray to be flattened:

Array.prototype.push.apply(dateArray,
  getDates(new Date(tijden[i]['begin']), 
           new Date(tijden[i]['eind']))
);

As it stands now, you just rewrite dateArray at each step of for loop.

---

A sidenote: this...

element = tijden[i];
tijden[i] = element;

... makes exactly zero sense: at least one of these lines (most probably the latter) is redundant. Remove this - and code becomes easier to read:

var element, currDates;
for (var i = 0, i < length; i++) {
  element = tijden[i];
  currDates = getDates(new Date(element.begin), new Date(element.eind));
  Array.prototype.push.apply(dateArray, currDates);
}