how to generate dynamic json data with emacs (macros)?

Question

I was in a meeting yesterday where I was presenting a program that referenced a certain json file with data like this:

[
{
  id: 1,
  text: '...',
  ...
},
{
  id: 2,
  text: '...',
  ...
}
]

In total there were around 6 of these objects in the array. I was asked how the program would handle a set of 100 objects. I tried simply copying the objects several times, then realized that this would be useless for my program unless the id incremented for each object. Of course, I could write something in you-name-it programming language to create such a json file, but I suspected there must be some way of using an emacs macro to quickly generate such a list of objects on the fly. Is this so? What's the most emacs-y way of doing this?

Answer 1

You can just make a list and then encode it as json like this:

(require 'cl-lib)
(require 'json)
(json-encode (cl-loop for i to 100 collect (list (cons 'id i) (cons 'text "..."))))

That gives me this string:

[{"id":0,"text":"..."},{"id":1,"text":"..."},{"id":2,"text":"..."},{"id":3,"text":"..."},{"id":4,"text":"..."},{"id":5,"text":"..."},{"id":6,"text":"..."},{"id":7,"text":"..."},{"id":8,"text":"..."},{"id":9,"text":"..."},{"id":10,"text":"..."},{"id":11,"text":"..."},{"id":12,"text":"..."},{"id":13,"text":"..."},{"id":14,"text":"..."},{"id":15,"text":"..."},{"id":16,"text":"..."},{"id":17,"text":"..."},{"id":18,"text":"..."},{"id":19,"text":"..."},{"id":20,"text":"..."},{"id":21,"text":"..."},{"id":22,"text":"..."},{"id":23,"text":"..."},{"id":24,"text":"..."},{"id":25,"text":"..."},{"id":26,"text":"..."},{"id":27,"text":"..."},{"id":28,"text":"..."},{"id":29,"text":"..."},{"id":30,"text":"..."},{"id":31,"text":"..."},{"id":32,"text":"..."},{"id":33,"text":"..."},{"id":34,"text":"..."},{"id":35,"text":"..."},{"id":36,"text":"..."},{"id":37,"text":"..."},{"id":38,"text":"..."},{"id":39,"text":"..."},{"id":40,"text":"..."},{"id":41,"text":"..."},{"id":42,"text":"..."},{"id":43,"text":"..."},{"id":44,"text":"..."},{"id":45,"text":"..."},{"id":46,"text":"..."},{"id":47,"text":"..."},{"id":48,"text":"..."},{"id":49,"text":"..."},{"id":50,"text":"..."},{"id":51,"text":"..."},{"id":52,"text":"..."},{"id":53,"text":"..."},{"id":54,"text":"..."},{"id":55,"text":"..."},{"id":56,"text":"..."},{"id":57,"text":"..."},{"id":58,"text":"..."},{"id":59,"text":"..."},{"id":60,"text":"..."},{"id":61,"text":"..."},{"id":62,"text":"..."},{"id":63,"text":"..."},{"id":64,"text":"..."},{"id":65,"text":"..."},{"id":66,"text":"..."},{"id":67,"text":"..."},{"id":68,"text":"..."},{"id":69,"text":"..."},{"id":70,"text":"..."},{"id":71,"text":"..."},{"id":72,"text":"..."},{"id":73,"text":"..."},{"id":74,"text":"..."},{"id":75,"text":"..."},{"id":76,"text":"..."},{"id":77,"text":"..."},{"id":78,"text":"..."},{"id":79,"text":"..."},{"id":80,"text":"..."},{"id":81,"text":"..."},{"id":82,"text":"..."},{"id":83,"text":"..."},{"id":84,"text":"..."},{"id":85,"text":"..."},{"id":86,"text":"..."},{"id":87,"text":"..."},{"id":88,"text":"..."},{"id":89,"text":"..."},{"id":90,"text":"..."},{"id":91,"text":"..."},{"id":92,"text":"..."},{"id":93,"text":"..."},{"id":94,"text":"..."},{"id":95,"text":"..."},{"id":96,"text":"..."},{"id":97,"text":"..."},{"id":98,"text":"..."},{"id":99,"text":"..."},{"id":100,"text":"..."}]