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Using the reduce function to return an array

rated 0 times [ 32] [ 4] / answers: 1 / hits: 106462 / 8 Years ago, tue, february 16, 2016, 12:00:00

Why is it that when I want to use the push function inside the reduce function to return a new array I get an error. However, when I use the concat method inside the reduce function, it returns a new array with no problem.

All I'm trying to do is pass an array to the reduce function and return the same array.

var store = [0,1,2,3,4];



var stored = store.reduce(function(pV,cV,cI){

  console.log(pv: , pV);

  return pV.push(cV);

},[]);

This returns an error. But when I use concat:

var store = [0,1,2,3,4];



var stored = store.reduce(function(pV,cV,cI){

  console.log(pv: , pV);

  return pV.concat(cV);

},[]);

It returns the same array.

Any ideas why?

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irvingcarloe

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2 Years ago

answered 8 Years ago jennie · Accepted Answer

push returns the new length of the array.

What you need is the initially provided array.

So change the code as below.

var store = [0, 1, 2, 3, 4];



var stored = store.reduce(function(pV, cV, cI){

  console.log(pv: , pV);

  pV.push(cV);

  return pV; // *********  Important ******

}, []);

concat returns the new array combining the elements of the provided array and concatenated elements. so it works.