topic : understanding how to use promisify in Node.js
read this
callback => promise
The util.promisify() method basically takes a function as an input that follows the common Node.js callback style, i.e., with a (err, value) and returns a version of the same that returns a promise instead of a callback.
Promisify is used when you want to convert a callback function into a promise based function. Nowadays, is used promises because let the developers to write more structured code.
const fs = require("fs");
const util = require("util");
// readFile method is based on callback
fs.readFile("./app.js", (err, data) => {
if (err) console.error(err);
else console.log(data.toString());
});
console.log("=====================");
const readFile = util.promisify(fs.readFile);
// now readFile is based on promise
readFile("./app.js", { encoding: "utf-8" })
.then((val) => console.log(val))
.catch((err) => console.log(err))
.finally(() => console.log("all done"));
console.log("=====================");
// or use await/async
async function useWithAsyncAwait() {
const result = await readFile("./app.js", { encoding: "utf-8" });
console.log(result);
}
useWithAsyncAwait();
topic : understanding how to use promisify in Node.js
read this
reference