Return File Data With A Custom Function-CodePudding

I am building my own project (website) and I am trying to create a renderTemplate function to return HTML files but I don't how to return data from the file

Here is quick example of what I am doing

var file = require("fs")

const render = () => {
    file.readFile(`file.txt`, {encoding: "utf-8"}, (err, data) => {
        if (err) throw err
        return data
    })
}

console.log(render())

I made sure the file.txt exists, ran the code and got undefined in the output

CodePudding user response：

Because render doesn not return anything, and it can't return anything since you are using the asynchronous callback based version of readFile.

Or you use the sync version:

const fs = require("fs")

const render = () => fs.readFileSync(`file.txt`, {encoding: "utf-8"})

console.log( render() )

Or you use promise based async version that is better if you have multiple readings:

const fs = require("fs")

const render = () => fs.readFileAsync(`file.txt`, {encoding: "utf-8"})

render().then( data => console.log(data) )

CodePudding user response：

Since there is no return in your function, it returns undefined. You can try readFileSync

Example:

 const render = () => file.readFileSync("file.txt" , { encoding: "utf-8" });
 console.log(render())

 const render = () => {
   return new Promise((resolve, reject) => {
     file.readFile(`file.txt`, { encoding: "utf-8" }, (err, data) => {
        if (err) reject(err);
        resolve(data);
     });
   });  
 }; 

 render().then(console.log)