Extending Underscore.js - findOr

As good as underscore.js is, sometimes you want to add functions of your own, and you can, using the mixin() function.

_.mixin({
  capitalize : function(string) {
    return string.charAt(0).toUpperCase() + string.substring(1).toLowerCase();
  }
});
_("fabio").capitalize();
=> "Fabio"

findOr

Underscore has a find method that returns the first element of a collection that matches a supplied predicate. For example, it can be used to find the first even number in a set:

var isEven = function (num) {
  return num % 2 === 0;
}

_([1,2,3,4,5]).find(isEven);
=> 2

findOr is a function I mixed-in to underscore so that I could have find return a default value if no element matches the predicate.

_([1,2,3]).findOr(isEven, 'no even numbers');
=> 2

_([1,3]).findOr(isEven, 'no even numbers');
=> 'no even numbers'

The implementation, using underscore’s mixin function, is:

_.mixin({
  'findOr': function(list, iterator, defaultValue, context) {
    return this.find(list, iterator, context) || defaultValue;
  }
});

Try the executable demo on jsfiddle.