Node basic concepts and basic usage 2

 

 

 

## Node programming
1. Node terminal interaction:
```
node
>1+2
>3
```
Exit: ctrl+c twice
2. Callback function (blocking VS non-blocking)
```
Blocking:
var fs = require( "fs");

 

var data = fs.readFileSync('input.txt');

 

console.log(data.toString());
console.log("Program execution ends!");

 

output: text content
program execution ends
```` `
```
non-blocking
var fs = require("fs");

 

fs.readFile('input.txt', function (err, data) {
if (err) return console.error(err);
console.log(data.toString());
});

 

console.log("Program execution ends!");
Output: Program execution ends
Text content
```
Note: The first parameter is generally err