nodejs check if file is running on server or client code example

Example 1: node check if file exists

const fs = require("fs"); // Or `import fs from "fs";` with ESM
if (fs.existsSync(path)) {
    // Do something
}

Example 2: nodejs check if file is running on server or client

function is_server() {
   return ! (typeof window != 'undefined' && window.document);
}