Javascript Blocks #

Javascript blocks begin with the line ### javascript. That is, when the page-break marker (line starts with ###) has javacript after the triple hashes, the following block will be treated as Javascript instead of an HTTP request.

For example, consider the following sheet:

GET http://httpbun.com/get?id=1

### javascript

alert("ha")

###

GET http://httpbun.com/get?id=2

Here, we have two HTTP requests defined with a Javascript block in the middle. If we were to execute the first HTTP request, the Javascript block will not be evaluated. If we were to execute the second HTTP request, the Javascript will be evaluated before the HTTP request is made. This is because only the Javascript blocks that are above the request being executed, are evaluated.

Obviously, calling alert in a Javascript block here, although awesome, isn’t a whole lot useful. Prestige provides APIs that can be used within these Javascript blocks to setup template data (see Templating ), change proxy configuration, event handling (coming soon), etc. See the API reference for full details on the APIs available.

Evaluation Details #

This is a slightly advanced topic that is not essential to normal usage of Prestige.

The code inside the Javascript blocks is evaluated by first building a Function object out of it, and then calling that function.

For example, consider the following Javascript block:

### javascript
alert("hello there")

This is (roughly) converted into the following function:

async function () {
    alert("hello there")
}

This function is then called as await fn.call(context), where the context object is constructed specifically for this function and will be available as this inside the function body.

Since this is an async function we are building, you are free to use the await syntax to call upon any asynchronous tasks inside the Javascript blocks. Prestige will wait for this async function to resolve before proceeding.

Conclusion #

Javascript blocks provide real programming ability making Prestige sheets programmable environments. They also lend a lot of flexibility to power users in they way they can execute HTTP requests. Learn more about that in our Templating guide.