prof3ssorSt3v3/hello.txt

## hello.txt
Hey there!
Guten Tag.
Hur mår du?

## index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <h1>Error-First Callbacks</h1>
    <script>
      function someFunc(someVal, cb) {
        //sample function that accepts a callback
        let err = null;
        if (typeof someVal === 'string') {
          someVal = someVal.replace('hello', 'Howdy');
        } else {
          err = new TypeError('No string provided');
          err.typeProvided = typeof someVal;
        }
        cb(err, someVal);
      }

      try {
        someFunc('hello world', (err, response) => {
          //check first for an error
          if (err) throw err;
          console.log('SUCCESS', response);
        });
        someFunc(true, (err, response) => {
          //check first for an error
          if (err) throw err;
          console.log('SUCCESS', response);
        });
      } catch (err) {
        //handle the error
        let msg = err.name + '\n' + err.message + '\n';
        msg = msg.concat(err.typeProvided, ' sent instead');
        console.warn(msg);
      }
    </script>
  </body>
</html>

## main.js
// Error-First callback pattern
// Continuation-Passing style: callbacks are continuation functions

let fs = require('fs');

fs.readFile('./hello.txt', (err, data) => {
  //err could be null
  if (err) return err;

  //don't run this if err not null
  console.log(data);
});
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="UTF-8" />
	<meta name="viewport" content="width=device-width, initial-scale=1.0" />
	<title>Document</title>
	</head>
	<body>
	<h1>Error-First Callbacks</h1>
	<script>
	function someFunc(someVal, cb) {
	//sample function that accepts a callback
	let err = null;
	if (typeof someVal === 'string') {
	someVal = someVal.replace('hello', 'Howdy');
	} else {
	err = new TypeError('No string provided');
	err.typeProvided = typeof someVal;
	}
	cb(err, someVal);
	}

	try {
	someFunc('hello world', (err, response) => {
	//check first for an error
	if (err) throw err;
	console.log('SUCCESS', response);
	});
	someFunc(true, (err, response) => {
	//check first for an error
	if (err) throw err;
	console.log('SUCCESS', response);
	});
	} catch (err) {
	//handle the error
	let msg = err.name + '\n' + err.message + '\n';
	msg = msg.concat(err.typeProvided, ' sent instead');
	console.warn(msg);
	}
	</script>
	</body>
	</html>
	// Error-First callback pattern
	// Continuation-Passing style: callbacks are continuation functions

	let fs = require('fs');

	fs.readFile('./hello.txt', (err, data) => {
	//err could be null
	if (err) return err;

	//don't run this if err not null
	console.log(data);
	});