In Lodash.js/Underscore.js, how to add index for every element?

Question

Here is the input:

[{animal: "cat"}, {animal:"dog}}

And the output would be :

[{animal: "cat", idx: 1}, {animal: "dog", idx: 2}]

Does anyone have ideas about how to do this in Lodash/Underscore.js?

Answer 1

In Underscore:

You could use either .map or .each to iterate across every element in the target array you were looking to add indexes to. Then you could use _.extend to add the "idx" prop.

Working Example:

var data =  [{animal: "cat"}, {animal:"dog"}]

_.map(data, function(e, i) {
  return _.extend(e, {idx: i + 1});
});