Summing per type

JavaScript performance comparison

Revision 2 of this test case created

Preparation code

<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.4.2/underscore-min.js">
</script>
<script>
  Benchmark.prototype.setup = function() {
    // set up a 1 million item array
    var bigData = [],
        types = "ABCDEF".split(''),
        typesLength = types.length;
    _(1000000).times(function(i) {
      bigData.push({
        type: types[_.random(0, typesLength - 1)],
        val: _.random(1, 10)
      });
    });
  };
</script>

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Testing in unknown unknown
Test Ops/sec
Object Hash for Total Per Type
 
var totalPerType = {};
for (var i = 0, len = bigData.length; i < len; ++i) {
  totalPerType[bigData[i].type] = totalPerType[bigData[i].type] || 0;
  totalPerType[bigData[i].type] += bigData[i].val;
}
var out = _.map(totalPerType, function(sum, type) {
  return {
    'type': type,
    'total': sum
  };
});
 pending…
Without creating intermediate hash
 
var out = [];
for (var i = 0, len = bigData.length; i < len; ++i) {
  var totalObj = _.find(out, function(x) {
    return x.type == bigData[i].type;
  });
  if (!totalObj) out.push({
    'type': bigData[i].type,
    'total': bigData[i].val
  });
  else totalObj.total += bigData[i].val;
}
 pending…
Nevir's reduce solution
 
var summed_by_type = _(bigData).reduce(function(mem, d) {
  mem[d.type] = (mem[d.type] || 0) + d.val
  return mem
}, {});

out = _(summed_by_type).map(function(v, k) {
  return {
    type: k,
    total: v
  }
});
 pending…
lazyberezovsky's map-reduce solution
 
var groups = _(bigData).groupBy('type');

var out = _(groups).map(function(g, key) {
  return { 
     type: key, 
     val: _(g).reduce(function(m,x) { return m + x.val; }, 0) 
  };
});
 pending…
Object Hash for Total Per Type - single assignment
 
var totalPerType = {};
for (var i = 0, len = bigData.length; i < len; ++i) {
  totalPerType[bigData[i].type] += (totalPerType[bigData[i].type] || 0) + bigData[i].val;
}
var out = _.map(totalPerType, function(sum, type) {
  return {
    'type': type,
    'total': sum
  };
});
 pending…

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