Question

Given two arrays, one with keys, one with values:

keys = ['foo', 'bar', 'qux']
values = ['1', '2', '3']

How would you convert it to an object, by only using underscore.js methods?

{
   foo: '1', 
   bar: '2',
   qux: '3'
}

I’m not looking for a plain javascript answer (like this).

I’m asking this as a personal exercise. I thought underscore had a method that was doing exactly this, only to find out it doesn’t, and that got me wondering if it could be done.
I have an answer, but it involves quite a few operations. How would you do it?

Answer 1

What you need to use is the _.object method of underscore js.
If object method is not present in your version of underscore.js then you will have to manually add this method to it.

keys = ['foo', 'bar', 'qux']
values = ['1', '2', '3']
_.object = function(list, values) {
  if (list == null) return {};
  var result = {};
  for (var i = 0, l = list.length; i < l; i++) {
    if (values) {
      result[list[i]] = values[i];
    } else {
      result[list[i][0]] = list[i][1];
    }
  }
  return result;
};

console.log(_.object(keys, values))

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>