Question

Is it possible to combine Underscore’s filter and map? I currently have two separate function calls, but I’m wondering if I can make them more efficient by combining them into a single call, somehow.

Basically I have an array of country names – I want to filter them using a regex, then map the filtered results to an array of DataItem objects. This is my current code:

var filteredData = _.filter(allCountries, function(n, i){ 
  var re = RegExp("^" + searchString, "i");
  if (re.exec(n['country'].toLowerCase()) !== null) {
    return true;
  }
});
var mappedData = _.map(filteredData, function(n, i){ 
  return new DataItem(i, n['name'], n['budget']);
});

Any other tips for improved efficiency would also be gratefully received.

Answer 1

You can use each instead:

 result = []
_.each(array, function(elem) {
    if(elem.indexOf(search) == 0)
        result.push(...whatever...)

Also note that you don’t need a regular expression just to find out if a string starts with another one.