lodash calculate difference between array elements

Question

In javascript using lodash, I need a way to calculate the difference between array elements, for instance:

With an array of
[0,4,3,9,10]
I need to get the difference between each element.
output should be
[4,-1,6,1]

How would I do this using lodash?

In ruby it looks something like this:
ary.each_cons(2).map { |a,b| b-a }

Answer 1

One possible solution is with using _.map():

var arr = [0,4,3,9,10];

var result = _.map(arr, function(e, i) {
  return arr[i+1] - e;
});

result.pop();

document.write(JSON.stringify(result));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.9.3/lodash.min.js"></script>

Answer 2

You could do something do something like this:

var arr = [0, 4, 3, 9, 10];
var res = [];
_.reduce(_.rest(arr), function (prev, next) {
  res.push(next - prev);
  return next;
}, arr[0]);