What is the peculiarity of loading data via $.getJSON?

Question

JavaScript

I load json data from a file and pass it to a variable.

var tests;
var data = $.getJSON( "html.json", function() {
  tests = JSON.parse(data.responseText);
});

Then I process them through the lodash template engine.

var genListData = _.template(document.getElementById('list-template').innerHTML);
document.write(genListData(tests[1]));

When the data is not in a separate file, but immediately in a variable, then everything is fine, everything works.
var tests ={ some json };

But I don’t want to constantly flatter the script when updating the data. It's much more convenient to have a separate JSON file. Tell me, maybe I did not take into account something when uploading the file?

UPD// when reloading the page, I found that sometimes the file still has time to load and everything works, but this rarely happens.