the interesting bit in this code is the bit that goes

fetch("http://127.0.0.1:5000/api/open-kitty-location")

since this sends an http request to a local server… my flask app

another interesting part is

.then(r => r.json())

which takes the http response and parses it as JSON

Parsing JSON means converting a JSON-formatted string into a data structure, such as a dictionary or list, that can be easily manipulated in a programming language.

In simple terms, .then() in JavaScript is used to run a function after an asynchronous task, like fetching data, is successfully completed.

In layperson’s terms, .then(r => r.json()) takes the response from a web request and converts it into a JavaScript object that you can easily work with.

The .then(r => r.json()) method converts the response into a JavaScript object, typically an object or array, depending on the JSON structure returned by the web request.

appreciate that the second .then uses the result from the first .then

.then(data => alert(data.msg)) means that after successfully getting some data, it will show a pop-up alert displaying the message stored in the msg property of that data.

In this context, “data” is not a specific term but rather a placeholder name for the variable that holds the information returned from a web request. You can name it anything you like, as it simply represents the content being processed in the function.

<button id="kitty-location">open kitty</button>

<script>
document.getElementById("kitty-location").addEventListener("click", () => {
      fetch("http://127.0.0.1:5000/api/open-kitty-location?location=")
      .then(r => r.json())
});
</script>