Why is this so much slower in Ruby than in Node?

euler_methods.rb

def divisors_count(n)
  count = 0
  bound = Math.sqrt(n).floor
  if bound*bound == n
    count = 1
    bound -= 1
  elsif (bound+1)*(bound+1) == n 
    count = 1
  end
  (1..bound).each do |i|
    count += 2 if n%i == 0
  end
  return count
end

eulerMethods.js

exports.divisors_count = function (n) {
  var count = 0
  var bound = Math.floor(Math.sqrt(n))
  if (bound*bound == n) {
    count = 1;
    bound -= 1;
  }
  else if ((bound+1)*(bound+1) == n) {
    count = 1;
  }
  for(var i=1;i<=bound;i+=1) {
    if (n%i ==0) {count += 2}
  }
  return count;
}

problem12.js

var methods = require('./eulerMethods.js');

var problem12 = function() {
  var n=1;
  var triangle = 0;
  var divisors
  while (true) {
    triangle +=n;
    divisors=methods.divisors_count(triangle);
    if (divisors>=100) {
      console.log(triangle, divisors);
    }
    if (divisors >= 500) {return triangle}
    n += 1;
  }
}

console.log(problem12());

problem12.rb

require "./euler_methods"

def problem12
  n=1
  triangle = 0
  while true
    triangle +=n
    divisors=divisors_count(triangle)
    puts "#{triangle} #{divisors}" if divisors>=100
    return triangle if divisors >= 500
    n += 1
  end
end

puts problem12.inspect

quick test: varying speeds of math.sqrt is definitely not the problem.

JS:

$ cat sqrtTest.js
> console.log(Math.sqrt(987654321))
$ time node sqrtTest
> 31426.968052931865

real    0m0.048s
user    0m0.034s
sys 0m0.009s

Ruby:

$ cat sqrt_test.rb
> puts Math.sqrt(987654321)
$ time ruby sqrt_test.rb
> 31426.968052931865

real    0m0.014s
user    0m0.005s
sys 0m0.003s

More time tests:
Ruby:

$ cat sqrt_test.rb

i=0
while i<10000 do
  Math.sqrt(9876543210)
  i += 1
end

$ time ruby sqrt_test.rb 
real    0m0.018s
user    0m0.009s
sys     0m0.004s
$ vi sqrt_test.rb
$ cat sqrt_test.rb

i=0
while i<100000 do
  Math.sqrt(9876543210)
  i += 1
end

$ time ruby sqrt_test.rb 
real    0m0.043s
user    0m0.037s
sys     0m0.004s

JS:

$ cat sqrtTest.js

i=0;
while(i<10000) {
  Math.sqrt(9876543210);
  i += 1;
}

$ time node sqrtTest.js 
real    0m0.055s
user    0m0.040s
sys     0m0.008s
$ vi sqrtTest.js
$ cat sqrtTest.js

i=0;
while(i<100000) {
  Math.sqrt(9876543210);
  i += 1;
}
$ time node sqrtTest.js 
real    0m0.048s
user    0m0.039s
sys     0m0.008s