Useful Underscore.js Extensions

underscore.extensions.js

(function() {

  //
  // Iterates over an array of numbers and returns the sum. Example:
  //
  //    _.sum([1, 2, 3]) => 6
  //
  _.sum = function(obj) {
    if (!$.isArray(obj) || obj.length == 0) return 0;
    return _.reduce(obj, function(sum, n) {
      return sum += n;
    });
  }

})();

you should pull request for this. very useful.

With mixin:

_.mixin( {
    sum: function ( Object ) {
        if (
                !$.isArray( Object ) ||
                Object.length == 0 ) {
            return ( 0 )
        }
        return (
            _.reduce(
                Object, function ( Sum, Number ) {
                    return ( Sum += Number )
                } ) )
    }
} )

.... allows for _([1, 2, 3]).sum() => 6