Build a POS receipt printer in Node.js

Disclosure: I build Receiptful, the printing API used in this tutorial. The Node and Express parts apply whatever you print with. You have orders coming into your point of sale, and you want each one to print on the thermal printer at the counter. This is a complete walkthrough of a small Node service that does exactly that. By the end you will have an endpoint you can POST an order to and watch paper come out. There is nothing to install next to the printer for this tutorial to work, and no ESC/POS to write by hand. You send HTML, Receiptful prints it. Before you start You need two things from the console : A paired printer, which gives you a printer ID . If you have not done this yet, the getting started guide walks through it in a couple of minutes. An API key (the rf_live_… value), created under API keys and shown only once. On the code side you need Node 18 or newer, so that fetch is available globally with no extra dependency. We will use TypeScript, but the same code works in plain JavaScript if you drop the types. Put your credentials in the environment rather than in the source: export RECEIPTFUL_API_KEY = "rf_live_3f9c…" export RECEIPTFUL_PRINTER_ID = "42" Step 1: model the order Start with the shape of an order. Yours will have more fields, but this is enough to print a useful receipt: interface LineItem { name : string ; quantity : number ; unitPrice : number ; // in cents, to avoid float rounding } interface Order { id : number ; items : LineItem []; placedAt : Date ; } Keeping money in cents and formatting only at the edges saves you from the classic floating point rounding bugs that show up as a receipt total that is one cent off. Step 2: render the order as HTML This is the part that decides how the receipt looks. Receiptful converts the HTML you send into ESC/POS for your specific printer, so you get to lay a receipt out with tags you already know instead of byte codes. function money ( cents : number ): string { return " $ " + ( cents / 100 ). toFi