Write to file from static file in Node.JS Express by calling server side javaScript

Question

I have a node.js project and i can write to a file from the app.js file. App.js starts the server and runs the content of index.html in my public folder. The problem is that i can't write to a file from the javascript in the public folder, and i guess this is because all the javascript in there is client side. How do i call server side javascript so that i can do I/O?

Index.html - located in Public folder

 <html>
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 
  <title>test1</title>
</head>
<body>
    <button onclick="WriteToFile()">writie to file</button> <br>
    </body>
</html>

App.js

var express = require('express');
var bodyParser = require('body-parser');
var path = require('path');
var app = express();

// set static path
app.use(express.static(path.join(__dirname, 'public')));

app.listen(3000, function(){
    console.log('Server started on Port 3000...');
})

//How do i call this function or write to a file from index.html.
function WriteToFile(){
    fs = require('fs');
    fs.writeFile('helloworld.txt', 'The Function was called', function (err) {
    if (err) 
    return console.log(err);
    console.log('Wrote Hello World in file helloworld.txt, just check it');
});
}

Read about Ajax calls from the browser to your server. It's a way of making a request to your server from your client-side Javascript. You then implement a route on your server that receives the Ajax call and executes the desired code on the server. — jfriend00
– jfriend00, Commented Jul 3, 2018 at 21:04

gomes · Accepted Answer · 2018-07-03 20:27:31Z

1

How do i call server side javascript so that i can do I/O?

You don't. Never, ever.

If there is a separation between client and server side, there is a reason to it. Security mostly, but also a separation of concerns.

While node.js allows you to render views, it is still a back-end framework, and the back-end and generated front-end are not linked in any way. Even monolithic framework like Rails that make it seem as if there was just one block from both back-end and front-end are separate, they just have very good abstractions to hide the separation between the two.

You'll want to create a route in express that will execute said function.

app.get('/hello-world', function(){
// Insert your logic here
})

Then on your front-end, call this endpoint using either Axios (easier) or the fetch API (more boilerplate but native function, no need for an external module).

edited Jul 3, 2018 at 20:27

answered Jul 3, 2018 at 20:18

gomes

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