Templating #

Templating, in Prestige, refers to the feature of being able to write bits of Javascript in HTTP requests, and have those bits of Javascript be replaced with the result of evaluating that Javascript code. That definition might not seem like much but templating lends a lot of power for when writing HTTP requests in Prestige.

Before we get our hands dirty, an important point to note is that templating is different inside the headers section and the request body section. This distinction might seem unnecessary at first, but after having been using Prestige for almost a year, I can tell the needs of templating are very different when writing the body, compared to when writing the URL and headers. Prestige tries to provide the best solution for power users at the cost of making it slightly more complicated to new-comers.

Headers Section #

The templating syntax in the headers section is the same as that of Javascript’s standard template strings.

What does that mean? That means we can write interpolations in the headers section using the syntax ${1 + 2} and it will be replaced by the value of the expression (3 in this case). Consider the following example:

GET http://httpbun.com/get?answer=${2 * 21}

When we hit ((Ctrl+Enter)) on this, the request is actually sent to the URL http://httpbun.com/get?answer=42.

Internally, Prestige leverages your browser’s support for template strings to do the interpolation here. It doesn’t include a templating engine doing this thing, it’s just standard Javascript and your browser.

Body Section #

The body section is slightly less clever. First off, interpolations like the header section aren’t directly. It is instead treated like a static wall of text, just a bunch of characters to be sent as payload in the HTTP request. So in the following request, the ${2 * 21} is sent as is, not replaced by 42.

POST http://httpbun.com/post

answer=${2 * 21}&hero=Arthur

The magic in the body section begins with an = sign. Quite literally. If the first character of your request body is =, Prestige will expect a Javascript expression to follow and the result of that expression is used as the request payload. That’s it. Let’s look at a few examples to drive home the point. All requests below are identical. They all send the request body answer=42&hero=Arthur.

POST http://httpbun.com/post

= "answer=" + (2 * 21) + "&hero=Arthur"

###

POST http://httpbun.com/post

= `answer=${2 * 21}&hero=Arthur`

###

POST http://httpbun.com/post

= (() => {
    // Compute the answer here :)
    const answer = 2 * 21;
    return `answer=${answer}&hero=Arthur`;
})()

Have to admit, that’s awesome right there! But let’s sweeten it further eh? Guess what the following does?

POST http://httpbun.com/post
Content-Type: application/json

= {
    answer: 2 * 21,
    hero: "Arthur",
}

Yep, JSON! Since the expression after = evaluates to an Object, as opposed to a String (which was the case in the previous examples), Prestige will notice the Content-Type: application/json header and just stringify the object for you before sending it on its merry way as the request payload.

Additionally, this way of using an Javascript expression to build the body is also useful when you want to upload a file as part of the request. See our guide on the File Bucket for more details.

Conclusion #

This topic can be a bit daunting when you’re new to Prestige, but I urge you to not completely ignore it. You can get by in Prestige without ever having to deal with templating, but you’d be losing out on a lot of the power Prestige provides you. You can always check our page on Tips and Tricks to see some real-world examples of how this can be leveraged to make life easier.