Question

I have a array of objects – something like this:

[
  {"name" : "blar", "percentageTotal" : "10", "mostPopular" : "false", "leastPopular" : "false"}, 
  {"name" : "foo", "percentageTotal" : "40", "mostPopular" : "false", "leastPopular" : "false"}, 
  {"name" : "bar", "percentageTotal" : "50", "mostPopular" : "false", "leastPopular" : "false"}
]

What would the best way to iterate over the objects and update the “mostPopular” and “leastPopular” properties, based on the “percentageTotal” property?

Answer 1

In one pass find the index of the most and least popular items by max/min “percentageTotal” setting the most/least popular attributes to false, then set the most/least popular from the stored indices.

function updatePopularity(items) {
  // Find the min/max popularity by percentage total.
  var min=null, max=null, i;
  for (i=0; i<items.length; i++) {
    items[i].mostPopular = items[i].leastPopular = false;
    if (!max || (items[i].percentageTotal > max.pct)) {
      max = {idx:i, pct:items[i].percentageTotal};
    }
    if (!min || (items[i].percentageTotal < min.pct)) {
      min = {idx:i, pct:items[i].percentageTotal};
    }
  }
  // Set the most/least popular values.
  items[max[idx]].mostPopular = true;
  items[min[idx]].leastPopular = true;
}

This solution does not require the names to be unique. You might get a small performance boost by setting it=items[i] and using it instead.