How to make the data in the list add up in Google Earth Engine

Question

I am new in Earth Engine. Here is an image collection [img1,img2,img3,img4,img5]. I want to get List or image collection [img1+img2 , img2+img3, img3+img4, img4+img5]. I tried to complete the following code https://code.earthengine.google.com/1256826da91886b9242f29f20339d604 But the result is incorrect, I don't know where the error is. I try not to use for loops because I will have a lot of data to calculate.

var img1 = ee.Image(1);//3
var img2 = ee.Image(2);//5   
var img3 = ee.Image(3);//7   
var img4 = ee.Image(4);//9  
var img5 = ee.Image(5);
var image=ee.ImageCollection([img1,img2,img3,img4,img5]);

var list = image.toList(image.size());

var newList = list.slice(1);
print(list.size());
newList = newList.map(function(data) {
  data = ee.Image(data);
  var l = data.add(ee.Image(list.get(list.size().subtract(1))));
  return l;
})
print(newList) 

Answer 1

You can do it this way:

var img1 = ee.Image(1);
var img2 = ee.Image(2);
var img3 = ee.Image(3);
var img4 = ee.Image(4);
var img5 = ee.Image(5);

var image=ee.ImageCollection([img1,img2,img3,img4,img5]);

var list = image.toList(image.size());

var upList = list.slice(0, ee.Number(list.size()).subtract(1))
var downList = list.slice(1, list.size())

var outList = upList.zip(downList).map(function(listElem) {return ee.Image(ee.List(listElem).get(0)).add(ee.Image(ee.List(listElem).get(1)))})

Create upList with last element missing, downList with first element missing, zip them together to make a list of 2 element lists, and map a function to sum the images over that list.

I hope this helps.