Question

jQuery’s extend function has the option of recursive extension, which I use when creating json config files. I can see that underscore has an extend function, but it doesn’t even mention recursion. I assume this means it doesn’t recursively extend, but I thought I’d ask here before implementing it into my project and wasting a lot of time.

Answer 1

Your assumption is correct, Underscore’s extend does not recursively extend. The implementation is rather simple:

_.extend = function(obj) {
  each(slice.call(arguments, 1), function(source) {
    for (var prop in source) {
      obj[prop] = source[prop];
    }
  });
  return obj;
};

The most interesting part for you is what’s inside the for loop, a simple non-recursive assignment:

obj[prop] = source[prop];