simpleCopy_and_gc.js

var createArray = function (length) {
    var arr = [];
    for(var i = 0; i < length; ++i) {
      arr[i] = 0.1;
    }
    return arr;
  },
  length = 10000,
  arr1 = createArray(length),
  arr2 = createArray(length);

for (var i = 0; i < length; ++i) {
  for (var j = 0; j < length; ++j) {  
    arr1[i] = arr2[j];
  }
}
// this causes tones of Garbage collections over the course of execution:
// > ./d8 --trace_gc ./simpleGopy_and_gc.js
// [13738]  514 ms: Scavenge 1.7 (19.5) -> 0.8 (19.5) MB, 0.2 ms [Runtime::PerformGC].
// ... means every GC run collects 1MB of garbage.
// But as soon as you use any of the arrays. e.g.
// print(arr1[4]);
// the GC goes away.