We have built a web app like you describe, without any HTML coming from the server. We use pure.js (our lib), 3 things can happen when you debug: - the selecto

We have built a web app like you describe, without any HTML coming from the server. We use pure.js (our lib), 3 things can happen when you debug: - the selector is wrong, you get an exception - the data you want to read is not in the JSON, eg: an input value is blank - there is an error in a JS function, you can debug it like any JS code pure.js use only CSS selectors, HTML and JS/JSON.